<PAGE>   1
                                                                       
                                                                   Exhibit 10.46

                                                                       Execution

                            Cambridge, Massachusetts

    DATE OF LEASE EXECUTION: NOVEMBER 17, 1997 (To be completed by Landlord)




                                    ARTICLE I

                                 REFERENCE DATA



1.1  SUBJECTS REFERRED TO:

     Each reference in this Lease to any of the following subjects shall be
construed to incorporate the data stated for that subject in this Section 1.1:

LANDLORD:                     Richard L. Friedman, John L. Hall, II, J.
                              William Richardson and Marvin I. Droz
                              TRUSTEES OF KSA REALTY TRUST, under
                              Declaration of Trust dated June 11, 1982 and
                              recorded with the Middlesex South Registry
                              of Deeds in Book 14635, Page 542.

MANAGING AGENT:               CH & S Limited Partnership

LANDLORD'S & MANAGING         c/o Carpenter & Company, Inc.
AGENT'S ADDRESS:              20 University Road
                              Cambridge, MA 02138

LANDLORD'S
REPRESENTATIVE:               Gary J. Gianino

TENANT:                       Cambridge Energy Research Associates
                              Limited Partnership, a Delaware limited
                              partnership

TENANT'S ADDRESS (FOR
NOTICE AND BILLING):          20 University Road
                              Cambridge, Massachusetts 02138

TENANT'S REPRESENTATIVE:      Alice Barsoomian

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BUILDING ADDRESS:             20 University Road
                              Cambridge, Massachusetts 02138

TENANT'S SPACE:               Approximately 44,830 rentable square feet, of
                              which 21,515 rentable square feet are located on
                              the sixth floor, 21,515 rentable square feet are
                              located on the seventh floor and 1,800 rentable
                              square feet are located on the eighth floor, all
                              in the Office Component of the Charles Square
                              Site, all as shown on the floor plans attached
                              hereto as EXHIBIT A-2.


TOTAL RENTABLE FLOOR
AREA OF THE OFFICE
COMPONENT:                    109,295 rentable square feet

COMMENCEMENT DATE:            The earlier of (a) the date of Tenant's occupancy
                              of all or any portion of the Premises for the
                              conduct of its business or (b) the date that is
                              the later of (i) sixty (60) days after the
                              Delivery Date (as defined in Section 2.2) and (ii)
                              March 1, 1997. Promptly after the Commencement
                              Date has been determined, Landlord and Tenant
                              shall execute a certificate memorializing the
                              same.


SCHEDULED DELIVERY DATE:      January 2, 1998

TERM EXPIRATION DATE:         The date that is the last day of the sixtieth
                              (60th) full calendar month after the Commencement
                              Date, subject to Tenant's right to extend the Term
                              under Section 2.3 or terminate this Lease under
                              Section 2.4.

TERM:                         The period from the Delivery Date to the Term
                              Expiration Date, subject to Tenant's right to
                              extend the Term under Section 2.3 or terminate
                              this Lease under Section 2.4.

EXTENSION OPTION:             One (1) option to extend the Term for a period of
                              five (5) years, exercisable pursuant to the
                              provisions of Section 2.3 of this Lease.



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ANNUAL BASE RENT:             First six months
                              of Lease Year 1
                              (and any partial
                              calendar month after
                              the Commencement
                              Date):               $873,000 per annum, $72,800
                                                   per month (i.e., $29.12 per
                                                   rentable square foot per
                                                   annum for 30,000 rentable
                                                   square feet of the Premises)

                              Second six months
                              of Lease Year 1:     $1,122,450 per annum,
                                                   $93,537.50 per month (i.e.
                                                   $30.00 per rentable square
                                                   foot per annum for 37,415
                                                   rentable square feet of the
                                                   Premises)

                              Lease Year 2:        $1,344,900 per annum,
                                                   $112,075 per month (i.e.
                                                   $30.00 per rentable square
                                                   foot per annum for the entire
                                                   Premises)

                              Lease Year 3:        $1,389,730 per annum,
                                                   $115,810.83 per month (i.e.,
                                                   $31.00 per rentable square
                                                   foot per annum for the entire
                                                   Premises)

                              Lease Years 4
                              and 5:               $1,434,560 per annum,
                                                   $119,546.67 per month (i.e.
                                                   $32.00 per rentable square
                                                   foot per annum for the
                                                   entire Premises).

Notwithstanding the fact that Annual Base Rent during Lease Year 1 is calculated
based upon a portion of the entire Premises, Tenant shall have the right during
Lease Year 1 to occupy the entire Premises.

ANNUAL OPERATING COST         Actual Landlord's Operating Costs (as



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FOR 1997:                     defined in Section 4.2) for calendar year 1997

ANNUAL REAL ESTATE
TAXES FOR 1997:               Actual real estate taxes for calendar year 1997

ANNUAL ESTIMATED COST OF      $1.20 per annum per rentable square foot in
ELECTRICAL SERVICE TO         Tenant's Space (i.e., $53,796 per annum, $4,483
TENANT'S SPACE FOR 1997:      per month)

PERMITTED USES:               General Office use consistent with the operation
                              of a first class office building and no other use.

PUBLIC LIABILITY              BODILY INJURY: $1,000,000 per occurrence/
INSURANCE:                    $3,000,000 in the general aggregate
                              PROPERTY DAMAGE: $500,000


1.2 EXHIBITS.

     The exhibits listed below in this Section 1.2 are incorporated in this
Lease by reference and are to be construed as part of this Lease:

     EXHIBIT A       Plan of Charles Square Site.

     EXHIBIT A-1     Legal Description of Charles Square Site.

     EXHIBIT A-2     Plan Showing Tenant's Space.

     EXHIBIT B       Landlord's Services.

     EXHIBIT C       Rules and Regulations.

1.3  TABLE OF CONTENTS

ARTICLE I

     REFERENCE DATA .........................................................  1

ARTICLE II
     PREMISES AND TERM ......................................................  9
     2.1   PREMISES .........................................................  9



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     2.2   TERM ............................................................. 11
     2.3   OPTION TO EXTEND TERM ............................................ 11
             2.3.1  EXTENSION OPTION ........................................ 11
             2.3.2  EXTENSION RENT .......................................... 11
             2.3.3  PROCEDURE FOR ESTABLISHING EXTENSION RENT ............... 12
             2.3.4  CONDITIONS PRECEDENT TO EXTENSION OPTION ................ 15
     2.4   TENANT TERMINATION ............................................... 15

ARTICLE III

     CONSTRUCTION ........................................................... 16
     3.1   GENERAL PROVISIONS APPLICABLE TO CONSTRUCTION .................... 16
     3.2   REPRESENTATIVES .................................................. 17

ARTICLE IV

     RENT ................................................................... 17
     4.1   RENT ............................................................. 17
     4.2   OPERATING COSTS; ESCALATION ...................................... 18
     4.3   REAL ESTATE TAXES; ESCALATION .................................... 21
     4.4   ESTIMATED ESCALATION PAYMENTS .................................... 23
     4.5   CHANGE OF FISCAL YEAR ............................................ 25
     4.6   PAYMENTS ......................................................... 25

ARTICLE V

     LANDLORD'S  COVENANTS .................................................. 26
     5.1   LANDLORD'S COVENANTS DURING THE TERM ............................. 26
             5.1.1  BUILDING SERVICES ....................................... 26
             5.1.2  ADDITIONAL BUILDING SERVICES ............................ 27
             5.1.3  REPAIRS ................................................. 27
             5.1.4  QUIET ENJOYMENT ......................................... 27
             5.1.5  SIGNAGE ................................................. 28
             5.1.6  HOTEL CONFERENCE ROOMS .................................. 28
             5.1.7  SECURITY ................................................ 28
     5.2   INTERRUPTIONS .................................................... 28
     5.3   RECOVERY OF TENANT'S COSTS ....................................... 29
     5.4   LANDLORD'S INSURANCE ............................................. 30

ARTICLE VI

     TENANT'S COVENANTS ..................................................... 30
     6.1   TENANT'S COVENANTS DURING THE TERM ............................... 30
             6.1.1  TENANT'S PAYMENTS ....................................... 30
             6.1.2  REPAIRS AND YIELDING UP ................................. 31
             6.1.3  OCCUPANCY AND USE ....................................... 31
             6.1.4  RULES AND REGULATIONS.. ................................. 32



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             6.1.5  SAFETY APPLIANCES ....................................... 32
             6.1.6  ASSIGNMENT AND SUBLETTING ............................... 32
             6.1.7  INDEMNITY. .............................................. 33
             6.1.8  TENANT'S LIABILITY INSURANCE ............................ 34
             6.1.9  TENANT'S WORKER'S COMPENSATION INSURANCE ................ 34
             6.1.10 LANDLORD'S RIGHT OF ENTRY ............................... 34
             6.1.11 LOADING ................................................. 35
             6.1.12 LANDLORD'S COSTS ........................................ 35
             6.1.13 TENANT'S PROPERTY ....................................... 35
             6.1.14 LABOR OR MATERIALMEN'S LIENS ............................ 36
             6.1.15 CHANGES OR ADDITIONS .................................... 36
             6.1.16 HOLDOVER. ............................................... 37

ARTICLE VII

     CASUALTY AND TAKING .................................................... 37
     7.1   CASUALTY AND TAKING .............................................. 37
     7.2   RESERVATION OF AWARD ............................................. 39

ARTICLE VIII

     RIGHTS OF MORTGAGEE .................................................... 40
     8.1   PRIORITY OF LEASE ................................................ 40
     8.2   RIGHTS OF MORTGAGE HOLDERS; LIMITATION OF MORTGAGEE'S LIABILITY .. 41
     8.3   MORTGAGEE'S ELECTION ............................................. 43
     8.4   NO PREPAYMENT OR MODIFICATION, ETC ............................... 43
     8.5   NO RELEASE OR TERMINATION ........................................ 44
     8.6   CONTINUING OFFER ................................................. 44
     8.7   MORTGAGEE'S APPROVAL ............................................. 45

ARTICLE IX

     DEFAULT ................................................................ 46
     9.1   EVENTS OF DEFAULT ................................................ 46
     9.2   TENANT'S OBLIGATIONS AFTER TERMINATION. .......................... 47

ARTICLE X

     MISCELLANEOUS .......................................................... 49
     10.1  NOTICE OF LEASE .................................................. 49
     10.2  CONSTRUCTION ON ADJACENT PREMISES; EXPANSION ..................... 49




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     10.3  NOTICES FROM ONE PARTY TO THE OTHER .............................. 50
     10.4  BIND AND INURE ................................................... 50
     10.5  NO SURRENDER ..................................................... 51
     10.6  NO WAIVER, ETC ................................................... 51
     10.7  NO ACCORD AND SATISFACTION ....................................... 52
     10.8  CUMULATIVE REMEDIES .............................................. 52
     10.9  LANDLORD'S RIGHT TO CURE ......................................... 53
     10.10 ESTOPPEL CERTIFICATE ............................................. 53
     10.11 WAIVER OF SUBROGATION ............................................ 54
     10.12 ACTS OF GOD ...................................................... 55
     10.13 BROKERAGE ........................................................ 55
     10.14 SUBMISSION NOT AN OFFER .......................................... 56
     10.15 LANDLORD REMEDIES ................................................ 56
     10.16 APPLICABLE LAW AND CONSTRUCTION .................................. 57
     10.17 LIMITATION OF LANDLORD'S LIABILITY ............................... 58
     10.18 PARKING .......................................................... 58

ARTICLE XI

     LEASEHOLD IMPROVEMENTS; TENANT ALLOWANCE ............................... 59
     11.1  PLANS FOR LEASEHOLD IMPROVEMENTS ................................. 59
     11.2  CONSTRUCTION BY TENANT ........................................... 61
     11.3  TENANT ALLOWANCE ................................................. 62
     11.4  LANDLORD'S RIGHT TO TERMINATE LEASE PRIOR TO COMMENCEMENT DATE ... 63

ARTICLE XII

     RIGHT OF FIRST OFFER ................................................... 63
     12.1  RIGHT OF FIRST OFFER ............................................. 63



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1.4  DEFINITIONS.

     Certain terms used in this Lease are defined hereinafter in those Sections
in which the same are first mentioned. For convenience, certain other terms are
defined in this Section 1.4 as follows:

     1.4.1  The term "Building" shall mean the office building comprising the
Office Component and shown on EXHIBIT A.

     1.4.2  The term "Charles Square Site" shall mean the entire area shown on
EXHIBIT A (as the same may be expanded), as more particularly described on
EXHIBIT A-1, which is leased by Landlord herein pursuant to the Ground Lease.

     1.4.3  The term "Ground Lease" shall mean the ground lease from EMI
Cambridge Limited Partnership as ground lessor to Landlord as ground lessee
dated as of December 16, 1985, as amended.

     1.4.4  The term "Office Component" shall mean the building, consisting of
approximately 109,295 rentable square feet, located at the Building Address and
devoted to office and related uses.

     1.4.5  The term "rentable area" shall mean the area within demising walls,
measured from the glass line to the center line of demising partitions, together
with a pro rata share of the floor area of common facilities, which pro rata
share shall be the ratio of the floor area of Tenant Space to the total floor
area of the Office Component.

     1.4.6  The term "Lease Year" shall mean the period of twelve consecutive
calendar months beginning on the first day of the first full calendar month



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commencing on or after the Commencement Date and each successive period of
twelve consecutive calendar months thereafter.



                                   ARTICLE II

                                PREMISES AND TERM

2.1  PREMISES.

     Subject to and with the benefit of the provisions of this Lease and the
Ground Lease relating to the Charles Square Site, Landlord hereby leases to
Tenant, and Tenant leases from Landlord, Tenant's Space in the Building,
together with the telephone system and existing hard cable wiring presently in
Tenant's Space, excluding exterior faces of exterior walls. Tenant's Space, with
such exclusions and together with the Appurtenant Rights (as hereinafter
defined), is hereinafter referred to as the "Premises."

     As of the date of this Lease, Tenant occupies space on the third and fourth
floors of the Building under a lease dated as of July 27, 1995, as amended by
First Amendment to Lease dated as of September 26, 1995 and a side letter
agreement dated as of September 26, 1995 (said lease, as so amended, to be
referred to hereinafter as the "Existing Lease"). Landlord shall use diligent
efforts to deliver the Premises to Tenant on or before the Scheduled Delivery
Date, in broom clean condition, free of tenants and occupants, but otherwise
as-is, without representation or warranty. If Landlord fails to deliver the
Premises to Tenant on or before the Scheduled Delivery Date, this Lease shall
nevertheless continue in full force and effect and Landlord shall continue to
use diligent efforts so to deliver the Premises to



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Tenant. The Existing Lease shall terminate on the Commencement Date hereunder.
Landlord represents and warrants to Tenant that the term of the lease of the
current lessee of the Premises expires on December 31, 1997.

     Tenant shall have, as appurtenant to the Premises, the right (the
"Appurtenant Rights") to use in common with others entitled thereto: (a) the
driveways, service roads, ramps, sidewalks and walkways necessary for access to
the Charles Square Site and the Building, (b) the stairways, elevators, hallways
and lobbies necessary for access to Tenant's Space, (c) the restrooms located
outside of Tenant's Space on the sixth, seventh and eighth floors of the Office
Component, (d) the heating, ventilating, air-conditioning and other fixtures,
equipment and systems serving Tenant's Space in common with other portions of
the Charles Square Site, and (e) such other common areas and facilities of the
Charles Square Site as Landlord may provide or designate from time to time
(collectively, the "Common Areas").

     Landlord reserves the right from time to time, with reasonable advance
notice to Tenant except in the case of an emergency in which case no notice
shall be required, without material interference with Tenant's use and enjoyment
of the Premises or access thereto, (a) to install, repair, replace, use,
maintain and relocate for service to the Premises and to other parts of the
Building or either, building service fixtures and equipment wherever located in
the Building and (b) to alter or relocate any other common facilities; provided,
however, Landlord shall not reduce the rentable area of the Premises and shall
use reasonable efforts to perform such activities at times other than during
Tenant's ordinary business hours.



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2.2  TERM.

     To have and to hold for a period (the "Term") commencing on the date of
delivery of the Premises to Tenant in broom-clean condition, free of tenants and
occupants (the "Delivery Date") and continuing until the Term Expiration Date,
unless sooner terminated as provided in Section 2.4, Section 7.1 or in ARTICLE
IX, or extended as provided in Section 2.3. All of the terms and conditions of
this Lease, other than provisions relating to rent, shall apply during the
period between the Delivery Date and the Commencement Date.

2.3  OPTION TO EXTEND TERM.

     2.3.1  EXTENSION OPTION. Tenant shall have one (1) right and option to
extend the Term (the "Extension Option") with respect to all (but not just a
portion of) the Premises for one period of five (5) years (such period being
herein referred to as the "Extension Period"), exercisable by notice to Landlord
given not later than six (6) months prior to the expiration of the initial Term;
provided, however, that if Tenant fails to give timely notice to Landlord of
Tenant's exercise of the Extension Option, Tenant shall be deemed to have waived
its Extension Option rights. The word "Term" as used in this Lease includes the
Term, as extended, where the context so requires.

     2.3.2  EXTENSION RENT. All of the terms, provisions, covenants, and
conditions of this Lease shall continue to apply during the Extension Period,
except that the Annual Base Rent shall be the fair market rent being paid in the
vicinity of the Premises in Cambridge, Massachusetts, for leases with five-year
terms commencing




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as of the beginning of the Extension Period, for space comparable to the
Premises, used for the Permitted Uses and with rights and obligations comparable
to those of Tenant under this Lease (the "Extension Rent").

     2.3.3  PROCEDURE FOR ESTABLISHING, EXTENSION RENT. At least 150 days before
the end of the initial Term (the "Rent Notice Deadline"), Landlord shall give to
Tenant written notice (an "Extension Rent Notice") of the Extension Rent, as
calculated by Landlord. If Landlord fails so to notify Tenant at least 120 days
before the expiration of the Initial Term, Tenant shall have the right to give
written notice (also an "Extension Rent Notice") to Landlord of the Extension
Rent, as calculated by Tenant. If either Tenant or Landlord wishes to dispute
the other party's calculation of the Extension Rent, either party may give
written notice (a "Dispute Notice") to the other party within 30 days after
receiving such other party's Extension Rent Notice. Any Dispute Notice shall set
forth the Extension Rent, as calculated by the disputing party. If Landlord and
Tenant are unable to resolve any such dispute within seven days after such
Dispute Notice is given, such dispute shall be resolved according to the
following procedures.

            2.3.3.1  At any time after such seven-day period, Landlord and
Tenant each shall have the right, by written notice (a "Notice of Arbitration")
to the other, to demand arbitration of the calculation of the Extension Rent.
The party demanding arbitration shall appoint an arbitrator in the Notice of
Arbitration. With seven days after the Notice of Arbitration is given, the other
party shall by notice to the other party appoint a second arbitrator. If the
second arbitrator shall not have



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been appointed within such seven-day period, the position taken by the party
demanding arbitration shall be deemed to be the correct calculation of the
Extension Rent.

            2.3.3.2  Within seven days after the designation of the second
arbitrator, Landlord and Tenant shall submit their respective positions with
respect to the calculation of the Extension Rent to the two arbitrators.
Thereafter, the two arbitrators shall conduct such hearings and investigations
as they deem appropriate and shall, within fourteen days after the designation
of the second arbitrator, determine the correct calculation of the Extension
Rent. The arbitrators, or either of them, shall give notice of such resolution
(or notice of their inability to reach agreement, as the case may be) to the
parties within said fourteen-day period, and the agreement, if any, of the two
arbitrators shall be binding upon the parties to this Lease.

            2.3.3.3  If the two arbitrators are unable to reach an agreement
within such fourteen-day period, the two arbitrators shall, within fourteen days
after the designation of the second arbitrator, designate a third arbitrator. If
the two arbitrators shall fail to agree upon the designation of a third
arbitrator within said fourteen-day period, then they or either of them shall
give notice of such failure to agree to Landlord and Tenant within such
fourteen-day period and, if Landlord and Tenant fail to agree upon the selection
of such third arbitrator within seven days after the arbitrators give such
notice, then either party on behalf of both may apply to the president of the
Greater Boston Real Estate Board or, on his or her failure, refusal or




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inability to act, to a court of competent jurisdiction, for the designation of
such third arbitrator.

            2.3.3.4  Within seven business days after the designation of the
third arbitrator, the parties shall submit their respective positions with
respect to the calculation of the Extension Rent to the third arbitrator.
Thereafter, the third arbitrator shall conduct such hearings and investigations
as he or she may deem appropriate and shall, within fourteen days after the date
of the designation of the third arbitrator, determine the correct calculation of
the Extension Rent. Within such fourteen day period, the third arbitrator shall
give notice of such resolution to Landlord and Tenant and the third arbitrator's
determination shall be binding upon Landlord and Tenant.

            2.3.3.5  All arbitrators shall be qualified real estate
professionals who shall have had at least ten years of experience appraising
first-class buildings substantially similar to the Office Component in the
Greater Boston area. Landlord and Tenant shall each be entitled to present
evidence to the arbitrators in support of their respective positions. The
arbitrators shall not make any determination inconsistent with the terms of this
Lease. The arbitrators shall not have the power to add to, modify or change any
of the provisions of this Lease. The determination of the arbitrator(s), as
provided above, shall be conclusive and shall have the same force as a judgment
in a court of competent jurisdiction. Judgment on the determination made by the
arbitrator(s) under the foregoing provisions may be entered in any court of
competent jurisdiction.



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            2.3.3.6  Each party shall pay the fees, costs and expenses of the
arbitrator appointed by such party and of the attorneys and expert witnesses of
such party and one-half of the other fees, costs and expenses of arbitration
properly incurred under this Lease.

            2.3.3.7  None of the foregoing shall be construed so as to extend
the date by which Tenant must exercise its extension option or entitle Tenant to
revoke its exercise of such option if exercised.

     2.3.4  CONDITIONS PRECEDENT TO EXTENSION OPTION. Notwithstanding any
contrary provision of this Section 2.3 or any other provision of this Lease, the
Extension Option and any exercise by Tenant of the Extension Option shall be
void and of no force or effect unless on the date Tenant notifies Landlord that
it is exercising the Extension Option and on the date of commencement of the
Extension Period (i) this Lease is in full force and effect; and (ii) Tenant is
not in default of any of its obligations under this Lease after the giving of
any required notice and the expiration of any applicable grace period.

2.4  TENANT TERMINATION OPTION.

     2.4.1  Tenant shall have the right and option, exercisable by notice
delivered to Landlord at any time during the first thirty (30) full calendar
months of the Term, to terminate this Lease, such termination to be effective on
the date that is the last day of the thirty-sixth (36th) full calendar month of
the Term (the "Termination Date"), provided that (a) at the time of Tenant's
exercise there exists no default by Tenant under this Lease which continues
after the giving of any required notice and



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the expiration of any applicable grace period, and (b) Tenant delivers to
Landlord with its exercise notice a certified check payable to Landlord in an
amount equal to the sum of (i) $225,000 and (ii) six (6) months' of Annual Base
Rent and additional rent for the Premises in effect at the time of such
exercise. Said termination payment shall not relieve Tenant of its obligation to
pay rent hereunder for the remaining six months of the Term. If Tenant delivers
such notice and makes such payment to Landlord, this Lease and all of the
obligations of Landlord and Tenant shall terminate as of the Termination Date as
if such date were the date of the original expiration of the Term of this Lease.



                                   ARTICLE III

                                  CONSTRUCTION

3.1  GENERAL PROVISIONS APPLICABLE TO CONSTRUCTION.

     All construction work required or permitted by this Lease shall be done in
a good and workmanlike manner and in compliance with all applicable laws and all
lawful ordinances, regulations and orders of governmental authority and insurers
of the Building. Landlord may inspect the work of the Tenant at reasonable times
and promptly shall give notice of observed defects. Landlord will not approve
any construction, alterations, or additions requiring unusual expense to readapt
the Premises to normal office use on lease termination or increasing the cost of
construction, insurance or taxes on the Building or of Landlord's services
called for by Section 5.1 of this Lease unless Tenant first gives assurances
acceptable to Landlord that such readaptation will be made prior to such
termination without




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expense to Landlord and makes provisions acceptable to Landlord for payment of
such increased cost. Landlord will also disapprove any alterations or additions
requested by Tenant which in Landlord's reasonable opinion would be harmful to
the Building or its tenants. All changes and additions shall be part of the
Building except Tenant's trade fixtures, equipment and personal property and
such items as by writing at the time of approval the parties agree either shall
be removed by Tenant on termination of this Lease or shall be removed or left at
Tenant's election.

3.2  REPRESENTATIVES.

     Each party authorizes the other to rely in connection with their respective
rights and obligations under this ARTICLE III upon approval and other actions on
the party's behalf by Landlord's Representative in the case of Landlord or
Tenant's Representative in the case of Tenant or by any person designated in
substitution or addition by notice to the party relying.



                                   ARTICLE IV

                                      RENT

4.1  RENT.

     Commencing on the Commencement Date, Tenant shall pay to Landlord rent at
an annual rate equal to the Annual Base Rent, without any offset or reduction,
which rent shall be paid in equal installments of 1/12th of the Annual Base
Rent, in advance on the first day of each calendar month included in the Term,
but for any portion of a calendar month at the beginning or end of the Term, the
monthly



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installment shall be prorated based on the number of days in such calendar month
falling within the Term.

4.2  OPERATING COSTS; ESCALATION.

     Tenant shall pay to Landlord, as additional rent, Operating Cost Escalation
(as defined below), if any, on or before the thirtieth day following receipt by
Tenant of Landlord's Statement (as defined below). Within 120 days after the
end of Landlord's fiscal year ending during the Term and after Lease
termination, Landlord shall render a statement ("Landlord's Statement") in
reasonable detail and according to generally accepted accounting practices
certified by Landlord and showing for the preceding fiscal year or fraction
thereof, as the case may be, Landlord's Operating Costs. As used in this Lease,
"Landlord's Operating Costs" shall mean all of Landlord's costs and expenses
paid in operating, managing, repairing, replacing and maintaining the Office.
Component or the Charles Square Site generally.

     EXCLUDING (notwithstanding any provision of this Lease to the contrary) the
interest and amortization of principal and other charges relating to mortgages
for the Building and the Charles Square Site or leasehold interests therein; the
cost of special services rendered to tenants (including Tenant) for which a
special charge is made; leasehold improvements which are made in connection with
the preparation of any portion of the Charles Square Site for occupancy by a new
tenant or which are not provided generally for the benefit of tenants of the
Charles Square Site; costs, expenses or charges properly chargeable to a
particular tenant; efforts to lease portions of the Charles Square Site or to
procure tenants for the Charles Square Site,



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<PAGE>   19
including advertising and leasing commissions and attorneys' fees; depreciation
of any component of the Charles Square Site; repairs and replacements arising
out of a fire or other casualty occurring at the Charles Square Site; fees,
fines or penalties arising out of Landlord's breach of any obligations
(contractual or at law), including attorneys' fees; costs associated with vacant
space; wages and benefits of any employee, contractor or agent, except to the
extent included below; services which benefit only the Hotel Component or Retail
Component, as defined in the Ground Lease, of the Charles Square Site, without
any direct benefit to the Office Component; fees for licenses, permits or
inspections which are not part of routine maintenance, do not benefit Tenant or
tenants of the Office Component generally or result from the negligence of
Landlord or any other tenant; environmental compliance, testing or remediation;
compliance by Landlord with laws existing as of the date of this Lease,
including without limitation the Americans with Disabilities Act; sculpture,
paintings and other works of art; capital improvements (as defined under
generally accepted accounting principles), except to the extent included below;
and repairs necessary to cure defects in the construction of the Charles Square
Site.

     BUT INCLUDING, without limitation: expenses of any proceedings for
abatement of real estate taxes and assessments with respect to any fiscal year
or fraction of a fiscal year; premiums for insurance covering the Office
Component or the Charles Square Site generally; compensation and all fringe
benefits, worker's compensation insurance premiums and payroll taxes paid by
Landlord to, for or with respect to Carpenter & Company's Vice-President for
Finance and Development and all persons



                                      -19-

<PAGE>   20
at or below the level of building manager engaged in the operating, maintaining
or cleaning of the Building and the Charles Square Site, but in all cases
adjusted so that the percentage of such wages and benefits allocated to the
Charles Square Site equals the percentage of such person's working time for
Landlord devoted to the Charles Square Site; all utility charges not billed
directly to tenants by Landlord or the utility; payments to independent
contractors under service contracts for cleaning, operating, managing,
maintaining and repairing the Building and the Charles Square Site; management
fees (which payments may be to affiliates of Landlord) provided such fees do not
exceed market rates; rent paid by the managing agent or imputed cost equal to
the loss of rent by Landlord for making available to the managing agent space
for a Building office on the ground floor or above (provided that the rent, or
the imputed cost, is comparable to the rent charged for similar space in the
Building); costs of new capital improvements (as opposed to replacements of
existing capital items) made to (a) reduce operating expenses, (b) comply with
laws enacted after the date hereof or (c) maintaining the Office Component as a
first-class office building, provided such costs shall be amortized over the
useful life of the improvement in question utilizing a commercially reasonable
discount rate; and all other reasonable and necessary expenses paid in
connection with the cleaning, operating, managing, maintaining and repairing of
the Building and the Charles Square Site, or either. With respect to Landlord's
Operating Costs relating to the Charles Square Site (or any part thereof other
than solely to the Office Component), Landlord shall allocate to the Office
Component a portion of such costs and expenses which shall be reasonable



                                      -20-

<PAGE>   21
and which shall take into consideration the benefits received by the Office
Component with respect to such expenses. Any operating costs which were incurred
for the sole benefit or necessity of the Office Component shall be allocated
solely to the Office Component.

     "Operating Cost Escalation" for any fiscal year or fraction thereof shall
be equal to the difference, if any, between

     (a) the product of Landlord's Operating Costs for such fiscal year or
fraction thereof and a fraction, the numerator of which shall be the rentable
area of Tenant's Space and the denominator of which shall be one-half of the
Total Rentable Floor Area of the Office Component plus one-half of the average
number of such square feet as are occupied during such fiscal year or fraction
thereof, and

     (b) the product of the Annual Operating Costs for 1997 and a fraction, the
numerator of which shall be the rentable area of Tenant's Space and the
denominator of which shall be the Total Rentable Floor Area of the Office
Component.

4.3  REAL ESTATE TAXES; ESCALATION

     The term "real estate taxes" as used above shall mean for any fiscal year
or portion thereof all taxes of every kind and nature and installments and
interest on assessments for public betterments or public improvements assessed
by any governmental authority on the Charles Square Site, the Building and
improvements, or both, which the Landlord shall become obligated to pay in such
fiscal year or portion thereof because of or in connection with the ownership,
leasing and operation of the Charles Square Site, the Building and improvements,
or both, subject to the



                                      -21-

<PAGE>   22
following: There shall be excluded from such taxes all income taxes, personal
property taxes, excess profits taxes, excise taxes, franchise taxes and estate,
succession, inheritance and transfer taxes, provided, however, that if at any
time during the Term the present system of ad valorem taxation of real property
shall be changed so that in lieu of the whole or any part of the ad valorem tax
on real property, there shall be assessed on Landlord a capital levy or other
tax on the gross rents received with respect to the Charles Square Site, the
Building and improvements, or both, or a federal, state, county, municipal or
other local income, franchise, excise, single business or similar tax,
assessment, levy or charge (distinct from any now in effect) measured by or
based, in whole or in part, upon any such gross rents, then any and all of such
taxes, assessments, levies or charges, to the extent so measured or based, shall
be deemed to be included within the term "real estate taxes."

     In the case of real estate taxes becoming due and payable in any tax year
during the Lease Term, a portion of the real estate taxes shall be allocated to
the Office Component in accordance with the allocation for the Office Component
for the real estate taxes set forth in the invoice for real estate taxes or an
advisory letter from the tax assessor for the City of Cambridge which
establishes the allocation of real estate taxes among the various components of
the Charles Square Site. In the event the invoice for the real estate taxes does
not specify the portion of the total real estate taxes attributable to the
Office Component and the Landlord, after due diligence, cannot obtain a current
advisory letter from said tax assessor, the allocation for the



                                      -22-

<PAGE>   23
Office Component will be determined by Landlord acting in its reasonable
discretion, and, if appropriate, will be based on the then most recent advisory
letter. The amount so allocated is hereinafter "Office Component Taxes."

     Tenant shall pay to Landlord, as additional rent, Real Estate Tax
Escalation (as defined below), if any, on or before the thirtieth day following
receipt by Tenant of a statement from Landlord showing the amount of Real Estate
Tax Escalation ("Landlord's Tax Statement").

     "Real Estate Tax Escalation" shall be equal to the difference, if any,
between

     (a) the product of Office Component Taxes and a fraction, the numerator of
which shall be the rentable area of Tenant's Space and the denominator of which
shall be one-half of the Total Rentable Floor Area of the Office Component plus
one-half of the average number of such square feet of rentable area as are
occupied in the Office Component during such fiscal year or fraction thereof and

     (b) the product of the Annual Real Estate Taxes For 1997 and a fraction,
the numerator of which shall be the rentable area of Tenant's Space and the
denominator of which shall be the Total Rentable Floor Area of the Office
Component.

4.4  ESTIMATED ESCALATION PAYMENTS.

     If, with respect to any fiscal year or fraction thereof during the Term,
Landlord reasonably estimates that Tenant shall be obligated to pay Operating
Cost Escalation or Real Estate Tax Escalation, then Tenant shall pay, as
additional rent, on the first day of each month of such fiscal year and each
ensuing fiscal year thereafter, "Estimated Monthly Escalation Payments" equal to
1/12th of the sum of the




                                      -23-

<PAGE>   24
Operating Cost Escalation and Real Estate Tax Escalation for the respective
fiscal year set forth on the most recent reasonable written estimate provided by
Landlord to Tenant (the "Estimate"). In the event of an overpayment or
underpayment by Tenant on account of Operating Cost Escalation or Real Estate
Tax Escalation, an appropriate adjustment shall be made, (i) for Operating Cost
Escalation, within 30 days after Landlord's Statement is delivered to Tenant and
(ii) for Real Estate Tax Escalation, within 30 days after Landlord's Tax
Statement is delivered to Tenant. If such adjustment arises out of an
overpayment by Tenant, Tenant shall receive such adjustment as a credit against
payments of rent or additional rent due under this Lease or, upon the expiration
or termination of this Lease, by a payment from Landlord to Tenant. Landlord may
adjust such Estimated Monthly Escalation Payment from time to time and at any
time during a fiscal year by delivering an updated Estimate to Tenant, and
Tenant shall pay, as additional rent, on the first day of each month following
receipt of Landlord's notice thereof, the adjusted Estimated Monthly Escalation
Payment.

     Notwithstanding any other provision of this Section 4.4, if the Term
expires or is terminated as of a date other than the last day of a fiscal year,
then for such fraction of a fiscal year at the end of the Term, Tenant's last
payment to Landlord under Sections 4.2 and 4.3 shall be made on the basis of
Landlord's best estimate of the items otherwise includable in Landlord's
Statement and Landlord's Tax Statement and shall be made on or before the later
of (a) 10 days after Landlord delivers such estimate to Tenant or (b) the last
day of the Term, with an appropriate payment or



                                      -24-

<PAGE>   25
refund to be made upon submission of Landlord's Statement or Landlord's Tax
Statement, as applicable.

4.5  CHANGE OF FISCAL YEAR

     Landlord shall have the right from time to time to change the periods of
accounting under this Lease to any annual period other than the initial fiscal
year and, upon any such change, all items referred to in this Section 4.5 shall
be appropriately apportioned. In all Landlord's Statements and Landlord's Tax
Statements rendered under, this Section 4.5, amounts for periods partially
within and partially without the accounting periods shall be appropriately
apportioned and any items which are not determinable at the time of such
Statements shall be included therein on the basis of Landlord's reasonable
estimate and, with respect thereto, Landlord shall render promptly after such
determination is possible a supplemental Landlord's Statement or Landlord's Tax
Statement, and appropriate adjustment shall be made according thereto. All
Landlord's Statements and Landlord's Tax Statements shall be prepared on an
accrual basis of accounting.

4.6  PAYMENTS.

     All payments of Annual Base Rent and additional rent shall be made to
Managing Agent, or to such other person as Landlord may from time to time
designate in writing to Tenant. If any installment of Annual Base Rent or
additional rent or on account of leasehold improvements is paid more than five
days after the due date thereof, at Landlord's election, it shall bear interest
from the due date to the date paid at a rate equal to the average prime
commercial rate from time to time



                                      -25-

<PAGE>   26
established by the three largest national banks in Boston, Massachusetts from
such due date, but in no event less than an annual rate equal to 14% percent,
which interest shall be immediately due and payable as further additional rent.

4.7  TENANT'S RIGHT TO AUDIT LANDLORD'S BOOKS.

     Within 30 days after delivery of Landlord's statement of Landlord's
Operating Costs, upon the prior written request of Tenant, Tenant shall be
permitted to examine, in the office of Landlord's Managing Agent, the books and
records ("Books") relating to the calculation of Operating Cost Escalation and
Real Estate Tax Escalation, and have conducted (by an accountant of its
selection reasonably approved by Landlord) an audit of Landlord's Statement and
Landlord's Operating Costs. Landlord shall make all Books readily available for
such examination. Any such audit shall be done at Tenant's expense. To the
extent any such audit discloses a discrepancy in Landlord's Statement, after
Landlord's verification of such discrepancy, Landlord shall adjust Landlord's
Statement and the Estimated Monthly Escalation Payment accordingly.



                                    ARTICLE V

                              LANDLORD'S COVENANTS

5.1  LANDLORD'S COVENANTS DURING THE TERM.

     Landlord covenants during the Term:

     5.1.1  BUILDING SERVICES - To furnish, through Landlord's employees or
independent contractors, the services listed in EXHIBIT B, but the use of
freight



                                      -26-

<PAGE>   27
elevators shall be scheduled through Landlord's Representative with reasonable
advance notice;

     5.1.2  ADDITIONAL BUILDING SERVICES - To furnish, through Landlord's
employees or independent contractors, reasonable additional Building operation
services upon reasonable advance request of Tenant at equitable rates from time
to time established by Landlord to be paid by Tenant, but Landlord shall not
impose an additional charge on Tenant for heat, ventilation and air conditioning
after normal business hours;

     5.1.3  REPAIRS - Except as otherwise provided in ARTICLE VII of this Lease,
to perform such maintenance, to make such repairs to the Common Areas, roof,
exterior walls, floor slabs, other structural components, the heating,
ventilation, air conditioning and other mechanical systems and the other common
facilities of the Building as may be necessary to keep them in good condition
and working order; to keep all exterior driveways, service roads, ramps,
sidewalks and walkways on the Charles Square Site free of ice and snow; and to
comply with all laws, regulations and orders of governmental authorities
applicable to the Building or the Charles Square Site generally (as
distinguished from laws, regulations and orders applicable to Tenant's use of
the Premises); and

     5.1.4  QUIET ENJOYMENT - That Tenant, upon paying the rent and performing
its obligations hereunder, shall peacefully and quietly have, hold and enjoy the
Premises throughout the Term, with access 24 hours per day, 7 days per week, 52
weeks per year, without any manner of hindrance or molestation (including




                                      -27-

<PAGE>   28
transmission of noise, other than noise customarily associated with office
premises, from other parts of the Building) from Landlord or anyone claiming
under Landlord, subject however to all the terms and provisions hereof, and to
the terms of the Ground Lease.

     5.1.5  SIGNAGE. Subject to Landlord's prior written approval, Tenant shall
have the right, at its sole cost and expense, to place appropriate custom
signage on the entry doors to the Premises. Landlord, at its sole cost and
expense, shall include Tenant's name on the lobby directory.

     5.1.6  HOTEL CONFERENCE ROOMS. Tenant shall be entitled to contract with
the Charles Square Hotel for use of conference rooms and guest rooms at
preferred corporate rates.

     5.1.7  SECURITY. Landlord shall provide security for the Building,
including without limitation monitoring by security officers at all times,
patrols by security officers after normal business hours and a card-key access
system for after-hours entry into the building which records the card number for
later review.

5.2  INTERRUPTIONS.

     Landlord shall not be liable to Tenant for any compensation or reduction of
rent by reason of inconvenience or annoyance or for loss of business arising
from power losses or shortages or from the necessity of Landlord's entering the
Premises for any of the purposes in this Lease authorized or for repairing the
Premises or any portion of the Building or Lot. In case Landlord is prevented or
delayed from making any repairs, alterations or improvements, or furnishing any
service or



                                      -28-

<PAGE>   29
performing any other covenant or duty to be performed on Landlord's part, by
reason of any cause reasonably beyond Landlord's control, Landlord shall not be
liable to Tenant therefor, nor, except as expressly otherwise provided in
ARTICLE VII, shall Tenant be entitled to any abatement or reduction of rent by
reason thereof, nor shall the same give rise to a claim in Tenant's favor that
such failure constitutes actual or constructive, total or partial, eviction from
the Premises. Landlord shall use reasonable efforts to avoid inconvenience to
Tenant arising from interruptions in services and to restore such services and
make related repairs as expeditiously as is practicable.

     Landlord reserves the right to stop any service or utility system when
necessary by reason of accident or emergency or until necessary repairs have
been completed. Except in case of emergency repairs, Landlord will give Tenant
reasonable advance notice of any contemplated stoppage and will use reasonable
efforts to avoid unnecessary inconvenience to Tenant by reason thereof.

     Landlord also reserves the right to institute such policies, programs and
measures as may be necessary, required or expedient for the conservation or
preservation of energy or energy services or as may be necessary or required to
comply with applicable codes, rules, regulations or standards.

5.3  RECOVERY OF TENANT'S COSTS.

     In the event (i) Tenant successfully enforces against Landlord its rights
under this Lease or (ii) Tenant is sued by Landlord or joined in a suit against
Landlord and it is found that Tenant is not liable and Landlord is liable,
Landlord shall pay Tenant



                                      -29-

<PAGE>   30
all of its reasonable costs and expenses, including without limitation
reasonable attorneys' fees, incurred by or imposed upon Tenant in connection
with such enforcement or suit.

5.4  LANDLORD'S INSURANCE.

     Landlord shall maintain, with responsible companies qualified to do
business in Massachusetts, fire and other casualty insurance covering all
buildings and improvements on the Charles Square Site, in amounts not less than
100 percent of the replacement cost of such buildings and improvements, with
extended coverage endorsements.



                                   ARTICLE VI

                               TENANT'S COVENANTS

6.1  TENANT'S COVENANTS DURING THE TERM.

     Tenant covenants during the Term and such further time as Tenant occupies
any part of the Premises:

     6.1.1  TENANT'S PAYMENTS - To pay when due (a) all Annual Base Rent and
additional rent, (b) all taxes which may be imposed on Tenant's personal
property in the Premises (including, without limitation, Tenant's fixtures and
equipment) regardless to whomever assessed, (c) the Annual Estimated Cost of
Electrical Service to Tenant's Space and all other charges by public utilities
for telephone and other utility services (including service inspections
therefor) rendered to the Premises not otherwise required hereunder to be
furnished by Landlord without charge and not consumed in connection with any
services required to be furnished by Landlord



                                      -30-

<PAGE>   31
without charge and (d) as additional rent, all charges of Landlord for services
rendered pursuant to Section 5.1.2 hereof;

     6.1.2  REPAIRS AND YIELDING UP - Except as otherwise provided in ARTICLE
VII and Section 5.1.3 of this Lease, to keep the Premises in good order, repair
and condition, reasonable wear and tear and damage by fire, casualty or eminent
domain only excepted; and at the expiration or termination of this Lease
peaceably to yield up the Premises and all changes and additions therein in such
order, repair and condition, first removing all goods and effects of Tenant and
any items, the removal of which is required by agreement or specified herein to
be removed at Tenant's election and which Tenant elects to remove, and repairing
all damage caused by such removal and restoring the Premises and leaving them
clean and neat;

     6.1.3  OCCUPANCY AND USE - Continuously from the Commencement Date, to use
and occupy the Premises only for the Permitted Uses; not to injure or deface the
Premises, Building, or the Charles Square Site; and not to permit in the
Premises any use thereof which is offensive, contrary to law or ordinances
(including, without limitation, City of Cambridge anti-smoking ordinances), or
which creates a nuisance or invalidates or increases the premiums for any
insurance on the Building or its contents (the Landlord representing and
warranting to Tenant that the use of the Premises for the Permitted Uses shall
not by itself invalidate or increase the premiums for any insurance) or liable
to render necessary any alteration or addition to the Building;



                                      -31-

<PAGE>   32
     6.1.4  RULES AND REGULATIONS - To comply with the Rules and Regulations set
forth in EXHIBIT C and all other reasonable Rules and Regulations hereafter made
by Landlord, of which Tenant has been given notice, which Rules and Regulations
shall be applicable to all office tenants in the Building, for the care and use
of the Building and the Charles Square Site, it being understood that Landlord
shall not be liable to Tenant for the failure of other tenants of the Building
to conform to such Rules and Regulations;

     6.1.5  SAFETY APPLIANCES - To keep the Premises equipped with all safety
appliances required by law or ordinance or any other regulation of any public
authority because of any use made by Tenant and to procure all licenses and
permits so required because of such use and, if requested by Landlord, to do any
work so required because of such use, it being understood that the foregoing
provisions shall not be construed to broaden in any way Tenant's Permitted Uses;

     6.1.6  ASSIGNMENT AND SUBLETTING - Not without the prior written consent of
Landlord to assign this Lease, to make any sublease, or to permit occupancy of
the Premises or any part thereof by anyone other than Tenant, provided, however,
that with respect to any proposed assignment or subletting after Lease Year 1,
so long as (a) the proposed subtenant or assignee is a reputable person or
entity which satisfies Landlord's reasonable financial review for a subtenant or
assignee of the space in question, (b) Tenant remains liable in the Lease, and
(c) Tenant gives Landlord reasonable advance notice of such sublease or
assignment, Landlord's consent shall not be unreasonably withheld, delayed or
conditioned; as additional rent to



                                      -32-

<PAGE>   33
reimburse Landlord promptly for reasonable legal and other expenses incurred by
Landlord in connection with any request by Tenant for consent to assignment or
subletting; no assignment or subletting shall affect the continuing primary
liability of Tenant (which, following assignment, shall be joint and several
with the assignee); no consent to any of the foregoing in a specific instance
shall operate as a waiver in any subsequent instance. Notwithstanding any
provision of this Lease to the contrary, Tenant shall have the right to assign
this Lease or sublet any portion of the Premises to any business organization
controlled by, controlling, or under common control with Tenant or which is the
successor to Tenant by merger or through the sale of all or substantially all of
Tenant's assets (an "Affiliate"), provided Tenant demonstrates to Landlord's
reasonable satisfaction that the creditworthiness of the Affiliate is at least
equal to the greater of Tenant's creditworthiness (a) on the date hereof or (b)
on the date of such assignment or sublease.

     Notwithstanding the foregoing provisions of this Section 6.1.6, Tenant
covenants not to enter into any sublease the rental of which is based in whole
or in part on the net revenues, net income or profits derived by any tenant
within the meaning of Section 856(d)(2)(A) of the Internal Revenue Code of 1954,
as amended.

     6.1.7  INDEMNITY - To defend, with counsel reasonably acceptable to
Landlord, save harmless and indemnify Landlord from any liability for injury,
loss, accident or damage to any person or property and from any claims, actions,
proceedings and expenses and costs in connection therewith (including, without
implied limitation, counsel's reasonable fees): (i) arising from the omission,
fault, willful act, negligence



                                      -33-

<PAGE>   34
or other misconduct of Tenant or from any use made or thing done or occurring on
the Premises not due to the negligence or willful misconduct of Landlord or (ii)
resulting from the failure of Tenant to perform and discharge its covenants and
obligations under this Lease;

     6.1.8  TENANT'S LIABILITY INSURANCE - To maintain public liability
insurance on the Premises in amounts which shall, at the beginning of the Term,
be at least equal to the limits set forth in Section 1.1 of this Lease, and from
time to time during the Term, shall be for such higher limits, if any, as are to
Tenant's actual knowledge customarily carried in the area in which the Premises
are located on property similar to the Premises and used for similar purposes
and to furnish Landlord with certificates thereof;

     6.1.9  TENANT'S WORKER'S COMPENSATION INSURANCE - To keep all of Tenant's
employees working in the Premises covered by worker's compensation insurance in
statutory amounts and to furnish Landlord with certificates thereof;

     6.1.10 LANDLORD'S RIGHT OF ENTRY- To permit Landlord and Landlord's agents
entry upon reasonable advance notice to Tenant, except in the case of emergency
in which case no notice shall be required, to examine the Premises at reasonable
times and, if Landlord shall so elect, to make repairs or replacements
(provided, however, Landlord shall use reasonable efforts to prevent material
adverse effects on Tenant's use and enjoyment of the Premises); to remove, at
Tenant's expense, any changes, additions, signs, curtains, blinds, shades or the
like not consented to in writing; and to show the Premises to prospective
tenants during the 12 months preceding



                                      -34-

<PAGE>   35
expiration of the Term or the Extension Period (as applicable) and to
prospective purchasers and mortgagees at all reasonable times;

     6.1.11 LOADING - Not to place a load upon the Premises exceeding an average
rate of 50 pounds of live load per square foot of floor area; and not to move
any safe, vault or other heavy equipment in, about or out of the Premises except
in such manner and at such times as Landlord shall in each instance approve;
Tenant's business machines and mechanical equipment which cause vibration or
noise that may be transmitted to the Building structure or to any other leased
space in the Building shall be placed and maintained by Tenant in settings of
cork, rubber, spring or other types of vibration eliminators sufficient to
eliminate such vibration or noise;

     6.1.12 LANDLORD'S COSTS - In case Landlord shall be made party to any
litigation commenced by or against Tenant or by or against any parties in
possession of the Premises or any part thereof claiming under Tenant, which is
not exempted from Tenant's indemnity by the terms of Section 6.1.7, to pay, as
additional rent, all costs including, without implied limitation, counsel's
reasonable fees incurred by or imposed upon Landlord in connection with such
litigation and, as additional rent, also to pay all such costs and fees incurred
by Landlord in connection with the successful enforcement by Landlord of any
obligations of Tenant under this Lease;

     6.1.13 TENANT'S PROPERTY - All the furnishings, fixtures, equipment,
effects and property of every kind, nature and description of Tenant and of all
persons claiming by, through or under Tenant which, during the continuance of
this Lease or any occupancy of the Premises by Tenant or anyone claiming under
Tenant, may be on



                                      -35-

<PAGE>   36
the Premises or elsewhere in the Building or on the Charles Square Site shall be
at the sole risk and hazard of Tenant and, if the whole or any part thereof
shall be destroyed or damaged by fire, water or otherwise, by the leakage or
bursting of water pipes, steam pipes or other pipes, by theft or from any other
cause, no part of said loss or damage is to be charged to or to be borne by
Landlord unless due to the gross negligence or other similar misconduct of
Landlord;

     6.1.14 LABOR OR MATERIALMEN'S LIENS - To pay promptly when due the entire
cost of any work done on the Premises by Tenant, its agents, employees or
independent contractors; not to cause or permit any liens for labor or materials
performed or furnished in connection therewith to attach to the Premises; and
immediately to discharge Coy payment, bond or other method) any such liens which
may so attach;

    6.1.15 CHANGES OR ADDITIONS - Not to make any non-structural changes or
alterations to the Premises without Landlord's prior written consent, which
consent shall not be unreasonably withheld; not to make any structural changes
or additions to the Premises without Landlord's prior written consent, provided
that Tenant shall reimburse Landlord for all reasonable costs incurred by
Landlord in reviewing Tenant's proposed changes or additions, and provided
further that, in order to protect the functional integrity of the Building, all
such changes and additions shall be performed by contractors selected from a
list of approved contractors prepared by Landlord from time to time; and



                                      -36-

<PAGE>   37
     6.1.16 HOLDOVER - To pay to Landlord 150% of the total of the Annual Base
Rent and additional rent then applicable for each month or portion thereof
Tenant shall retain possession of the Premises or any part thereof after the
termination of this Lease, whether by lapse of time or otherwise, and also to
pay all damages sustained by Landlord on account thereof, consequential and
otherwise; the provisions of this subsection shall not operate as a waiver by
Landlord of any right of re-entry provided in this Lease.



                                   ARTICLE VII

                               CASUALTY AND TAKING

7.1  CASUALTY AND TAKING.

     In case during the Term all or any substantial part of the Premises,
Building or the Charles Square Site, or any one or more of them, are (i) damaged
materially by fire or any other cause or by action of public or other authority
in consequence thereof or (ii) taken by eminent domain or Landlord receives
compensable damage by reason of anything lawfully done in pursuance of public or
other authority and as a consequence all or any substantial part of the
Premises, Building or Charles Square Site are damaged materially, this Lease
shall terminate at Landlord's election, which may be made, notwithstanding
Landlord's entire interest may have been divested, notice to Tenant within 30
days after the occurrence of the event giving rise to the by election to
terminate, which notice shall specify the effective date of termination which
shall be not less than 30 nor more than 60 days after the date of notice of such
termination and a just proportion of the Annual Base Rent and additional rent



                                      -37-

<PAGE>   38
according to the nature and extent of the injury and the effect on Tenant's use
and enjoyment of the Premises shall be abated from and after the occurrence of
the event giving rise to the election to terminate. If in any such case the
Premises, Building or the Charles Square Site, are rendered unfit for use and
occupation and the Lease is not so terminated, Landlord shall use due diligence
to put the Premises, Building or the Charles Square Site, or, in case of a
taking, what may remain thereof (excluding any items installed or paid for by
Tenant which Tenant may be required or permitted to remove) into substantially
the same condition that existed before such fire, casualty or taking to the
extent permitted by the net award of insurance or damages available to Landlord,
and a just proportion of the Annual Base Rent and additional rent according to
the nature and extent of the injury shall be abated until the Premises, Building
or the Charles Square Site, or such remainder shall have been put by Landlord in
such condition; and in case of a taking which permanently reduces the area of
the Premises, Building or Lot, a just proportion of the Annual Base Rent and
additional rent shall be abated according to the nature and extent of the injury
and the effect on Tenant's use and enjoyment of the Premises for the remainder
of the Term and an appropriate adjustment shall be made to the Annual Operating
Expenses. If in any such case the Lease is not so terminated and the Premises,
Building or the Charles Square Site (or in the case of a taking, at least 90
percent thereof) have not been put into proper condition for use and occupation
within one year after the damage or taking occurs, or, in the reasonable
judgment of Landlord's architect expressed within 60 days of such fire, casualty
or taking, are not capable of



                                      -38-

<PAGE>   39
being put into such condition within one year, this Lease shall terminate at
Tenant's election, which may be made by notice to Landlord within ten (10) days
after expiration of such year or within ten (10) days after notice that the
damage cannot reasonably be repaired within one year, as the case may be, and
shall be effective on the date such notice is given and all of Tenant's
obligations hereunder shall then cease except to pay rent accrued prior to the
termination, as such rent shall have been reduced pursuant to this Section on
account of the damage or taking.

7.2  RESERVATION OF AWARD.

     Landlord reserves to itself any and all rights to receive awards made for
damages to the Premises, Building or the Charles Square Site and the leasehold
hereby created, or any one or more of them, accruing by reason of exercise of
eminent domain or by reason of anything lawfully done in pursuance of public or
other authority. Tenant hereby releases and assigns to Landlord all Tenant's
rights to such awards and covenants to deliver such further assignments and
assurances thereof as Landlord may from time to time request and hereby
irrevocably designates and appoints Landlord as its attorney in fact to execute
and deliver in Tenant's name and behalf all such further assignments thereof. It
is agreed and understood, however, that Landlord does not reserve to itself, and
Tenant does not assign to Landlord, any damages payable for (i) trade fixtures,
equipment and personal property installed by Tenant, or anybody claiming under
Tenant, at the Premises or (ii) relocation or business interruption expenses or
damages of a similar nature recoverable by Tenant from such authority in a
separate action.



                                      -39-

<PAGE>   40
                                  ARTICLE VIII

                              RIGHTS OF MORTGAGEE

8.1  PRIORITY OF LEASE.

     This Lease is and shall continue to be subject and subordinate to any
presently existing mortgage, ground lease or deed of trust of record covering
the Lot or Building or both (the "mortgaged premises"), provided that Landlord
shall use diligent efforts to obtain on Tenant's behalf a nondisturbance
agreement from the holders of any such mortgages, deeds of trust or ground
leases within sixty (60) days after the date hereof (which nondisturbance
agreement may be in the standard form used by such holders). The holder of any
such presently existing mortgage or deed of trust or lessor under any such
ground lease shall have the election to subordinate the same to the rights and
interests of Tenant under this Lease exercisable by filing with the appropriate
recording office a notice of such election, whereupon the Tenant's rights and
interests hereunder shall have priority over such mortgage, ground lease or deed
of trust.

     Unless the option provided for in the next following sentence shall be
exercised, this Lease shall be superior to and shall not be subordinate to, any
mortgage, deed of trust or other voluntary lien hereafter placed on the
mortgaged premises. The holder of any such mortgage, deed of trust or other
voluntary lien shall have the option to subordinate this Lease to the same,
provided that such holder enters into a nondisturbance and attornment agreement
with Tenant, under which the holder will agree to recognize the rights of Tenant
under this Lease and to



                                      -40-

<PAGE>   41
accept Tenant as tenant of the Premises under the terms and conditions of this
Lease in the event of acquisition of title by such holder through foreclosure
proceedings or otherwise and Tenant will agree to recognize the holder of such
mortgage or lessor under such ground lease as Landlord in such event, which
agreement shah be made to expressly bind and inure to the benefit of the
successors and assigns of Tenant and of the holder or ground lessor and upon
anyone purchasing the mortgaged premises at any foreclosure sale. Any such
mortgage or ground lease to which this Lease shall be subordinated may contain
such terms, provisions and conditions as the holder or ground lessor deems usual
or customary.

8.2  RIGHTS OF MORTGAGE HOLDERS; LIMITATION OF MORTGAGEE'S LIABILITY.

     The word "mortgage" as used herein includes mortgages, deeds of trust or
other similar instruments evidencing other voluntary liens or encumbrances and
modifications, consolidations, extensions, renewals, replacements and
substitutes thereof. The word "holder" shall mean a mortgage and any subsequent
holder or holders of a mortgage. Until the holder of a mortgage shall enter and
take possession of the Premises for the purpose of foreclosure, such holder
shall have only such rights of Landlord as are necessary to preserve the
integrity of this Lease as security. Upon entry and taking possession of the
Premises for the purpose of foreclosure, such holder shall have all the rights
of Landlord. Notwithstanding any other provision of this Lease to the contrary,
including without limitation Section 10.4, no such holder of a mortgage or
ground lessor shall be liable either as



                                      -41-

<PAGE>   42
mortgagee or as assignee to perform, or be liable in damages for failure to
perform, any of the obligations of Landlord unless and until such holder or
ground lessor shall enter and take possession of the Premises for the purpose of
foreclosure, and such holder or ground lessor shah not in any event be liable to
perform or for failure to perform the obligations of Landlord under Article III
of this Lease. Upon entry for the purpose of foreclosure, such holder or ground
lessor shall be liable to perform all of the obligations of Landlord (except for
the obligations under Article III of this Lease), subject to and with the
benefit of the provisions of Section 10.4 of this Lease, provided that a
discontinuance of any foreclosure proceeding shall be deemed a conveyance under
said provisions to the owner of the equity of the Premises.

     No holder of a mortgage on or ground lessor of Landlord's interest in the
Premises s hall (i) be bound by any modification of this Lease not made as
expressly provided for in this Lease or by any previous prepayment of more than
one month's rent, unless such modification or prepayment shall have been
expressly approved in writing by the holder of the superior mortgage or ground
lessor of the ground lease through or by reason of which the holder or ground
lessor shall have succeeded to the fights of Landlord; or (ii) be liable for the
performance of Landlord's covenants and agreements contained in this Lease
except to the extent of the holder's or ground lessor's ownership in the
Premises, and no other property of such holder shall be subject to levy,
attachment, execution or other enforcement procedure for the satisfaction of
Tenant's remedies.



                                      -42-

<PAGE>   43
8.3  MORTGAGEE'S ELECTION.

     Notwithstanding any other provision to the contrary contained in this
Lease, if prior to substantial completion of Landlord's obligations under
ARTICLE XI and Section 2.1.1, any holder of a first mortgage on the mortgaged
premises or ground lessor under a ground lease enters and takes possession
thereof for the purpose of foreclosing the mortgage or terminating the ground
lease, such holder or ground lessor may elect, by written notice given to Tenant
and Landlord at any time within 90 days after such entry and taking of
possession, not to perform Landlord's obligations under ARTICLE XI and/or
Section 2.1.1 and, in such event, such holder or ground lessor and all persons
claiming under it shall be relieved of all obligations to perform, and all
liability for failure to perform, said Landlord's obligations under ARTICLE XI
and/or Section 2.1.1, and Tenant may terminate this Lease and all its
obligations hereunder by written notice to Landlord and such holder or ground
lessor given within 30 days after the day on which such holder or ground lessor
shall have given its notice as aforesaid.

8.4  NO PREPAYMENT OR MODIFICATION, ETC.

     Tenant shall not pay Annual Base Rent, additional rent or any other charge
more than 10 days prior to the due dates thereof. No prepayment of Annual Base
Rent, additional rent or other charge, no assignment of this Lease and no
agreement to modify so as to reduce the rent, change the Term or otherwise
materially change the rights of Landlord under this Lease, or to relieve Tenant
or any Guarantor of any



                                      -43-
<PAGE>   44
obligations or liability under this Lease, shall be valid unless consented to in
writing by Landlord's mortgagees or ground lessors of record, if any.

8.5  NO RELEASE OR TERMINATION.

     No act or failure to act on the part of Landlord which would entitle Tenant
under the terms of this Lease, or by law, to be relieved of Tenant's obligations
hereunder or to terminate this Lease, shall result in a release or termination
of such obligations or a termination of this Lease unless (i). Tenant shall have
first given written notice of Landlord's act or failure to act to Landlord's
mortgagees or ground lessors of record, if any (provided Tenant has received
written notice of the identity and address of such mortgagees or ground
lessors), specifying the act or failure to act on the part of Landlord which
could or would give basis to Tenant's fights and (ii) such mortgagees or ground
lessors, after receipt of such notice, have failed or refused to correct or
cure the condition complained of within a reasonable time thereafter, but
nothing contained in this Section 8.5 shall be deemed to impose any obligation
on any such mortgagee or ground lessor to correct or cure any such condition.
"Reasonable time" as used above means and includes a reasonable time to obtain
possession of the mortgaged premises, if the mortgagee or ground lessor elects
to do so, and a reasonable time to correct or cure the condition if such
condition is determined to exist.

8.6  CONTINUING OFFER.

     The covenants and agreements contained in this Lease with respect to the
rights, powers and benefits of a mortgagee or ground lessor (particularly,
without



                                      -44-

<PAGE>   45
limitation thereby, the covenants and agreements contained in this ARTICLE VIII)
constitute a continuing offer to any person, corporation or other entity, which
by accepting or requiring an assignment of this Lease or by entry or foreclosure
assumes the obligations herein set forth with respect to such mortgagee or
ground lessor; such mortgagee and ground lessor are each hereby constituted a
party to this Lease as an obligee hereunder to the same extent as though its
name was written hereon as such; and such mortgagee or ground lessor shall be
entitled to enforce such provisions in its own name. Tenant agrees on request of
Landlord to execute and deliver from time to time any agreement which may
reasonably be deemed necessary to implement the provisions of this ARTICLE VIII.

8.7  MORTGAGEE'S APPROVAL.

     Landlord's and Tenant's obligations to perform their covenants and
agreements under this Lease are subject to the condition precedent that this
Lease approved by the current mortgagee of the Charles Square Site (Aetna Life
and be Casualty Company) and the lessor under the Ground Lease. Landlord shall
use diligent efforts to obtain such approvals. Unless Landlord notifies Tenant
within 45 days after the date hereof that the Lease has been disapproved, the
condition set forth in this Section 8.7 shall be deemed satisfied.






                                     -45-

<PAGE>   46
                                   ARTICLE IX

                                     DEFAULT


9.1  EVENTS OF DEFAULT.

     If any default by Tenant continues after notice, in case of the failure to
make payments of Annual Base Rent, additional rent, or any other monetary
obligation to Landlord, for more than 10 days or, in the case of any other
failure by Tenant to perform its obligations under this Lease, for more than 30
days and such additional time, if any, as is reasonably necessary to cure the
default if the default is of such a nature that it cannot reasonably be cured in
30 days and Tenant diligently endeavors to cure such default; or if Tenant
becomes insolvent, files a petition under any chapter of the U.S. Bankruptcy
Code, 11 U.S.C. 101 et seq., as it may be amended (or any similar petition under
any insolvency law of any jurisdiction), or if such petition is filed against
Tenant and is not dismissed within 60 days; or if Tenant proposes any
dissolution, liquidation, composition, financial reorganization or
recapitalization with creditors, makes an assignment or trust mortgage for the
benefit of creditors, or if a receiver, trustee, custodian or similar agent is
appointed or takes possession with respect to any property of Tenant and is not
dismissed within 60 days; or if the leasehold hereby created is taken on
execution or other process of law in any action against Tenant; then, and in any
such case, Landlord and the agents and servants of Landlord may, in addition to
and not in derogation of any remedies for any preceding breach of covenant,
immediately or at any time thereafter while such default continues and without
further notice exercise any and all remedies permitted




                                      -46-

<PAGE>   47
by state or federal law. Tenant hereby waives all statutory rights (including,
without limitation, rights of redemption, if any) to the extent such rights may
be lawfully waived and Landlord, without notice to Tenant but no earlier than
the expiration of the applicable cure period, may store Tenant's effects and
those of any person claiming through or under Tenant at the expense and risk of
Tenant and, if Landlord so elects, may sell such effects at public auction or
private sale and apply the net proceeds to the payment of all sums due to
Landlord from Tenant, if any, and pay over the balance, if any, to Tenant.

9.2  TENANT'S OBLIGATIONS AFTER TERMINATION.

     In the event that this Lease is terminated under any of the provisions
contained in Section 9.1 of this Lease or shall be otherwise lawfully terminated
for breach of any obligation of Tenant, Tenant covenants to pay forthwith to
Landlord, as liquidated damages, the present value of the excess of the total
rent reserved for the residue of the Term over the rental value of the Premises
for said residue of the Term, calculated using a commercially reasonable
discount rate. In calculating the rent reserved, there shah be included, in
addition to the Annual Base Rent and all additional rent, the value of all other
consideration agreed to be paid or performed by Tenant for said residue. Until
Landlord demands such liquidated damages, Tenant further covenants after any
such termination to pay punctually to Landlord all the sums and perform all the
obligations which Tenant covenants in this Lease to pay and to perform in the
same manner and to the same extent and at the same time as if this Lease had not
been terminated. In calculating the amounts to be paid by Tenant



                                      -47-
<PAGE>   48
under the next foregoing covenant, Tenant shall be credited with the net
proceeds of any rents obtained by Landlord by reletting the Premises, after
deducting all Landlord's expenses in connection with such reletting, including,
without implied limitation, all repossession costs, brokerage commissions, fees
for legal services and expenses of preparing the Premises for such reletting, it
being agreed by Tenant that Landlord may (i) relet the Premises or any part or
parts thereof for a term or terms which may at Landlord's option be equal to or
less than or exceed the period which would otherwise have constituted the
balance of the Term and may grant such concessions and free rent as Landlord in
its sole judgment considers advisable or necessary to relet the same and (ii)
make such alterations, repairs and decorations in the Premises as Landlord in
its sole judgment considers advisable or necessary to relet the same, and no
action of Landlord in accordance with the foregoing or failure to relet or to
collect rent under reletting shall operate or be construed to release or reduce
Tenant's liability as aforesaid; provided, however, that if Landlord uses or
permits any person or entity in control of, under common control with or
controlled by Landlord to use the Premises during any part of the balance of the
Term or Extended Term, no less than the fair rental value of the Premises during
such period of use shall be credited against all sums due from Tenant.

     Nothing contained in this Lease shall, however, limit or prejudice the
right of Landlord to prove and obtain in proceedings for bankruptcy or
insolvency by reason of the termination of this Lease an amount equal to the
maximum allowed by any statute or rule of law in effect at the time when, and
governing the proceedings in



                                      -48-
<PAGE>   49
which, the damages are to be proved, whether or not the amount be greater, equal
to or less than the amount of the loss or damages referred to above.



                                    ARTICLE X

                                  MISCELLANEOUS


10.1 NOTICE OF LEASE.

     Upon request of either party, both parties shall execute and deliver, after
the Term begins, a short form of this Lease in form appropriate for recording or
registration and, if this Lease is terminated before the Term expires, an
instrument in such form acknowledging the date of termination.

10.2 CONSTRUCTION ON ADJACENT PREMISES; EXPANSION.

     If any excavation, alteration, addition, repair, or other building
operation shall be about to be made or shall be made on the Premises, the
Building or the Lot or on any premises adjoining the Lot, Tenant shall permit
Landlord, its agents, employees, licensees and contractors, with reasonable
advance notice to Tenant, except in the case of emergency, in which case no
notice shall be required, to enter the Premises and to shore the foundations
and/or walls thereof, and to erect scaffolding and/or protective barricades
around and about the Premises (but not so as to preclude entry thereto) and to
do any act or thing necessary for the safety or preservation of the Premises;
provided, however, Landlord shall not materially interfere with Tenant's use and
enjoyment of the Premises. Tenant's obligations under this Lease shall not be
affected by any such construction or excavation work or any such shoring-up so
long as Landlord does not materially interfere with Tenant's use and enjoyment
of



                                      -49-
<PAGE>   50
the Premises. Provided Landlord does not interfere with Tenant's use and
enjoyment of the Premises, Landlord shall not be liable for any inconvenience,
disturbance, loss of business or any other annoyance arising from any such
construction, excavation shoring-up, scaffolding or barricades, but Landlord
shall use its best efforts so that such work will cause such little
inconvenience, annoyance and disturbance to Tenant as possible.

10.3 NOTICES FROM ONE PARTY TO THE OTHER.

     All notices required or permitted hereunder shall be in writing and
addressed, if to the Tenant, at Tenant's Address or such other address as Tenant
shall have last designated by notice in writing to Landlord, with a copy to
Testa, Hurwitz & Thibeault LLP, High Street Tower, 125 High Street, Boston,
Massachusetts 02110, Attention: Real Estate Department, and, if to Landlord, at
Landlord's Address or such other address as Landlord shall have last designated
by notice in writing to Tenant, with a copy by like means to Paul Jakubowski,
Esq., Hale and Dorr LLP, 60 State Street, Boston, Massachusetts 02109. Any
notice shall be deemed duly given three days after being mailed to such address
postage prepaid, registered or certified mail, return receipt requested, or when
delivered to such address by hand.

10.4 BIND AND INURE.

     The obligations of this Lease shall run with the land and this Lease shall
be binding upon and inure to the benefit of the parties hereto and their
respective successors and assigns, except that the Landlord named herein and
each successive owner of the Charles Square Site shall be liable only for the
obligations accruing



                                      -50-
<PAGE>   51
during the period of its ownership. The obligations of Landlord shall be binding
upon the assets of Landlord which comprise the Charles Square Site but not upon
other assets of Landlord. No individual partner, trustee, stockholder, officer,
director, employee or beneficiary of Landlord shall be personally liable under
this Lease and Tenant shall look solely to Landlord's interest in the Charles
Square Site in pursuit of its remedies upon an event of default hereunder, and
the general assets of the individual partners, trustees, stockholders, officers,
employees or beneficiaries of Landlord shah not be subject to levy, execution or
other enforcement procedure for the satisfaction of the remedies of Tenant, upon
an event of default hereunder.

10.5 NO SURRENDER.

     The delivery of keys to any employee of Landlord or to Landlord's agent or
any employee thereof shall not operate as a termination of this Lease or a
surrender of the Premises.

10.6 NO WAIVER, ETC.

     The failure of Landlord or of Tenant to seek redress for violation of, or
to insist upon the strict performance of, any covenant or condition of this
Lease or any of the Rules and Regulations referred to in Section 6.1.4 of this
Lease, whether heretofore or hereafter adopted by Landlord, shall not be deemed
a waiver of such violation nor prevent a subsequent act, which would have
originally constituted a violation, from having all the force and effect of an
original violation, nor shall the failure of Landlord to enforce any of said
Rules and Regulations against any other tenant in the Building be deemed a
waiver of any such Rules or Regulations. The



                                      -51-
<PAGE>   52
receipt by Landlord of Annual Base Rent or additional rent with knowledge of the
breach of any covenant of this Lease shall not be deemed a waiver of such breach
by Landlord, unless such waiver be in writing and signed by Landlord. No consent
or waiver, express or implied, by Landlord or Tenant to or of any breach of any
agreement or duty shall be construed as a waiver or consent to or of any other
breach of the same or any other agreement or duty.

10.7 NO ACCORD AND SATISFACTION.

     No acceptance by Landlord of a lesser sum than the Annual Base Rent and
additional rent then due shall be deemed to be other than on account of the
earliest installment of such rent due, nor shall any endorsement or statement on
any check or any letter accompanying any check or payment as rent be deemed as
accord and satisfaction, and Landlord may accept such check or payment without
prejudice to Landlord's right to recover the balance of such installment or
pursue any other remedy in this Lease provided.

10.8 CUMULATIVE REMEDIES.

     The specific remedies to which Landlord may resort under the terms of this
Lease are cumulative and are not intended to be exclusive of any other remedies
or means of redress to which it may be lawfully entitled in case of any breach
or threatened breach by Tenant of any provisions of this Lease. In addition to
the other remedies provided in this Lease, Landlord and Tenant each shall be
entitled to the restraint by injunction of the violation or attempted or
threatened violation of any of



                                      -52-
<PAGE>   53
the covenants, conditions or provisions of this Lease or to a decree compelling
specific performance of any such covenants, conditions or provisions.

10.9  LANDLORD'S RIGHT TO CURE.

      If Tenant shall at any time default in the performance of any obligation
under this Lease and such default should continue after notice and the
expiration of the applicable grace period, Landlord shall have the right, but
shall not be obligated, to enter upon the Premises and to perform such
obligation, notwithstanding the fact that no specific provision for such
substituted performance by Landlord is made in this Lease with respect to such
default. In performing such obligation, Landlord may make any payment of money
or perform any other act. All sums so paid by Landlord (together with interest
at the rate of four percent per annum in excess of the then average prime
commercial rate of interest being charged by the three largest national banks in
Boston, Massachusetts), and all necessary incidental costs and expenses in
connection with the performance of any such act by Landlord, shall be deemed to
be additional rent under this Lease and shall be payable to Landlord immediately
on demand. Landlord may exercise the foregoing rights without waiving any other
of its rights or releasing Tenant from any of its obligations under this Lease.

10.10 ESTOPPEL CERTIFICATE.

      Tenant agrees, from time to time upon not less than 15 days' prior written
request by Landlord, to execute, acknowledge and deliver to Landlord a statement
in writing certifying, to the extent true, that this Lease is unmodified and in
full force



                                      -53-
<PAGE>   54
and effect; that, to Tenant's knowledge, Tenant has no defenses, offsets or
counterclaims against its obligations to pay the Annual Base Rent and additional
rent and to perform its other covenants under this Lease; that, to Tenant's
knowledge, there are no uncured defaults of Landlord or Tenant under this Lease
(or, if there have been any modifications, that this Lease is in full force and
effect as modified and stating the modifications and, if there are any defenses,
offsets, counterclaims, or defaults of which Tenant has knowledge, setting them
forth in reasonable detail); and the dates to which the Annual Base Rent,
additional rent and other charges have been paid. Any such statement delivered
pursuant to this Section 10.10 shall be in a form reasonably acceptable to and
may be relied upon by any prospective purchaser or mortgagee of premises which
include the Premises or any prospective assignee of any such mortgagee.

10.11 WAIVER OF SUBROGATION.

      Any insurance carried by either party with respect to the Premises and
property therein or occurrences thereon shall include a clause or endorsement
denying to the insurer rights of subrogation against the other party to the
extent fights have been waived by the insured prior to occurrences of injury or
loss. Each party, notwithstanding any provisions of this Lease to the contrary,
hereby waives any fights of recovery against the other for injury or loss due to
hazards covered by insurance containing such clause or endorsement to the extent
of the indemnification received thereunder.



                                      -54-
<PAGE>   55
10.12 ACTS OF GOD.

      In any case where either party hereto is required to do any act, delays
caused by or resulting from Acts of God, war, civil commotion, fire, flood or
other casualty, labor difficulties, shortages of labor, materials or equipment,
government regulations, unusually severe weather or other causes beyond such
party's reasonable control shall not be counted in determining the time during
which work shall be completed, whether such time be designated by a fixed date,
a fixed time or a "reasonable time", and such time shall be deemed to be
extended by the period of such delay. Notwithstanding anything herein contained,
however, the provisions of this Section 10.12 shall not be applicable to
Tenant's obligation to pay rent under the provisions of Article IV, or its
obligations to pay any other sums, monies, costs, charges or expenses required
to be paid by the Tenant hereunder or to Tenant's right to terminate this Lease
pursuant to Section 7.1.

10.13 BROKERAGE.

      Landlord and Tenant represent and warrant that they have dealt with no
broker in connection with this transaction other than Carpenter and Company and
Landlord agrees to defend, indemnify and save Tenant harmless from and against
any and all cost, expense or liability for any compensation, commissions or
charges claimed by any broker or agent other than Carpenter and Company with
respect to Tenant's dealings in connection with this Lease.



                                      -55-
<PAGE>   56
10.14 SUBMISSION NOT AN OFFER.

      The submission of a draft of this Lease or a summary of some or all of its
provisions does not constitute an offer to lease or demise the Premises, it
being understood and agreed that neither Landlord nor Tenant shall be legally
bound with respect to the leasing of the Premises unless and until this Lease
has been executed by both Landlord and Tenant and a fully executed copy has been
delivered to each of them.

10.15 LANDLORD REMEDIES.

      In addition to Landlord's other remedies, Landlord shall have the right,
during the Term of this Lease, to impose upon Tenant a fine of fifty dollars
($50.00) per day for each and every violation by Tenant of reasonable rules and
regulations of Landlord, as such may be promulgated from time to time or for
breach of the terms of this Lease. Such fine may be imposed no sooner than one
(1) business day following written notice by Landlord to Tenant of the breach of
the rules or regulations or terms of this Lease, unless such breach by Tenant of
the rules and regulations or the terms of this Lease cannot be cured within such
one (1) business day period, in which case such fine may be imposed no sooner
than thirty (30) days following written notice by Landlord to Tenant of the
breach of the rules or regulations or the terms of this Lease, provided however,
that if Tenant does not commence to cure such breach of the rules and
regulations or terms of this Lease upon receipt of notice from Landlord and
diligently pursue the curing of the same



                                      -56-
<PAGE>   57
during such thirty (30) day period, such fine may be imposed during such thirty
(30) day period.

10.16 APPLICABLE LAW AND CONSTRUCTION.

      This Lease shall be governed by and construed in accordance with the laws
of the Commonwealth of Massachusetts. If any term, covenant, condition or
provision of this Lease or the application thereof to any person or
circumstances shall be declared invalid or unenforceable by the final ruling of
a court of competent jurisdiction having final review, the remaining terms,
covenants, conditions and provisions of this Lease and their application to
persons or circumstances shall not be affected thereby and shall continue to be
enforced and recognized as valid agreements of the parties, and in the place of
such invalid or unenforceable provision, there shall be substituted a like, but
valid and enforceable provision which comports to the findings of the aforesaid
court and most nearly accomplishes the original intention of the parties.

      There are no oral or written agreements between Landlord and Tenant
affecting this Lease. This Lease may be amended, and the provisions hereof may
be waived or modified, only by instruments in writing executed by Landlord and
Tenant.

      The titles of the several Articles and Sections contained herein are for
convenience only and shah not be considered in construing this Lease.

      Unless repugnant to the context, the words Landlord and Tenant appearing
in this Lease shall be construed to mean those named above and their



                                      -57-
<PAGE>   58
respective heirs, executors, administrators, successors and assigns, and those
claiming through or under them respectively. If there be more than one tenant,
the obligations imposed by this Lease upon Tenant shall be joint and several.

10.17 LIMITATION OF LANDLORD'S LIABILITY.

      Tenant agrees in all events to look solely to Landlord's interest in the
Charles Square Site for satisfaction of any claim against Landlord hereunder and
Tenant agrees that Tenant shall have no other recourse against Landlord, nor
shall Tenant have any recourse against (i) any other property or assets of
Landlord or (ii) the partners, trustees, beneficiaries, shareholders, employees,
officers, directors, agents or principals of Landlord or any of their property
or assets.

10.18 PARKING.

      Tenant and its employees, agents, contractors and invitees shall have the
right to use, on a non-exclusive basis, a number of parking spaces in the
parking garage on the Charles Square Site equal to two (2) parking spaces for
every 1,000 square feet of rentable area in Tenant's Space from time to time.
Tenant shall pay a monthly charge to Landlord on account of each parking space
so used in any month, which charge shall be equal to the then current market
rates. In addition, Landlord will provide Tenant with thirty (30) tandem parking
spaces at an initial rate of $90 per month per parking space during Lease Years
1 and 2, with increases thereafter at the same percentage as any increases in
standard parking rates in the parking garage. Tenant and its employees, agents,
contractors and invitees shall have access to said parking garage from the hours
of 6:00 A.M. to 1:00 A.M. only. Tenant shall not permit its



                                      -58-
<PAGE>   59
employees who have parking passes for the parking garage to share passes with
others who do not have passes, nor shall Tenant allow its employees to leave
vehicles in the parking garage over weekends or while they are traveling, it
being understood and agreed by Tenant that the parking garage is to be used for
purposes of daily commuting only.



                                   ARTICLE XI

                    LEASEHOLD IMPROVEMENTS; TENANT ALLOWANCE


11.1  PLANS FOR LEASEHOLD IMPROVEMENTS

      11.1.1 Tenant, at Tenant's sole cost and expense, shall cause to be
prepared and delivered to Landlord for Landlord's approval two sets of
preliminary plans and specifications ("preliminary plans ") for the renovations
and improvements to Tenant's Initial Space prepared by a registered architect.

      11.1.2 Following Landlord's approval of the preliminary plans, Tenant, at
Tenant's sole cost and expense, shall cause to be prepared and delivered for
Landlord's approval four sets of working drawings and specifications ("working
drawings") for the renovations and improvements to Tenant's Initial Space
prepared by a registered architect in conformity with the approved preliminary
plans and with Landlord's reasonable requirements and shall make any revisions
reasonably requested by Landlord and shah obtain Landlord's approval on or
before October 31, 1997; provided, however, that Landlord shall review the
working drawings and respond to Tenant within three business days of receipt of
said drawings and shall



                                      -59-
<PAGE>   60
not unreasonably withhold its approval of the working drawings. Landlord shall
evidence its approval by causing one set of such working drawings to be
initialed on its behalf and returned to the Tenant. Before beginning
construction of Leasehold Improvements in the Expansion Space, Tenant shall
cause to be prepared and delivered to Landlord four sets of working drawings for
the Expansion Space prepared by a registered architect and shall make any
revisions reasonably requested by Landlord and shall obtain Landlord's approval;
provided, however, Landlord shall review the working drawings and respond to
Tenant within three business days of receiving the working drawings and shall
not unreasonably withhold its approval of the working drawings. Landlord will
not approve any construction, alterations or additions requiring unusual expense
to readapt the Premises for office use on lease termination or unusually
increasing the cost of construction, insurance or taxes on the Office Component
or of Landlord's services unless Tenant first gives assurances acceptable to
Landlord that such readaptation will be made prior to such termination without
expense to Landlord and makes provisions acceptable to Landlord for payment of
such increased cost. Landlord will also disapprove any alterations or additions
requested by Tenant which will in Landlord's reasonable opinion be harmful to
the Office Component or other tenants. All changes and additions shall be part
of the Premises upon termination of the Lease unless Landlord and Tenant agree
otherwise in writing at the time of approval of such changes or additions.

      11.1.3 After Landlord's approval of the working drawings, no change shall
be made thereto except as provided in this Section 11.1.3:



                                      -60-
<PAGE>   61
             (i)    No change may be made by either party without the prior
                    written consent of the other (which shall not be
                    unreasonably withheld or delayed).

             (ii)   All architectural services necessitated shall be rendered by
                    Tenant's architect at the expense of the party requesting
                    the change; and

             (iii)  All construction work necessitated by any change shall be
                    performed by Tenant's contractor; if the change was
                    requested by Landlord, Tenant's Allowance (as hereinafter
                    defined) shall be adjusted to reflect any increase in the
                    cost of the Leasehold Improvements (as defined below)
                    resulting therefrom.

11.2  CONSTRUCTION BY TENANT.

      All work described in the working drawings (the "Leasehold Improvements")
shall be performed by Tenant's general contractor, the identity of which must be
approved by Landlord, which approval shall not be unreasonably withheld. The
construction of the Leasehold Improvements shah be coordinated with any work
being performed by Landlord in such manner as to maintain harmonious labor
relations and not to damage or, in Landlord's reasonable opinion, unreasonably
interfere with operations of or require the making of any structural changes to
the Office Component. Before commencing construction of the Leasehold
Improvements, Tenant at its own expense shall provide any necessary appropriate
riders for fire and extended coverage and comprehensive general public liability
and property damage insurance covering the risks during the course of such work
and certificates showing that necessary Workmen's Compensation and Employer's
Liability Insurance has been taken out to protect all employees engaged in the
work during the course of such



                                      -61-
<PAGE>   62
construction. The provisions of Sections 3.1 and 6.1.7 of this Lease shall apply
to any work done by Tenant or any agent, employee, invitee or visitor of Tenant
under this Section.

11.3  TENANT ALLOWANCE.

      Tenant shall be entitled to an allowance for construction of the Leasehold
Improvements in an amount not to exceed $450,000, to be requisitioned, if at
all, within eighteen (18) months after the date hereof. Such allowance shall be
paid as follows:

      (a)   Up to $100,000 of the allowance shall be paid by Landlord to Tenant
(or, at Tenant's election made by notice to Landlord, to Tenant's contractor or
architect directly) after the date hereof but prior to substantial completion of
the Leasehold Improvements, for costs and expenses of the Leasehold Improvements
incurred by Tenant, as evidenced by invoices and other supporting documentation
reasonably acceptable to Landlord, within ten (10) days after request therefor
by Tenant;

      (b)   Within ten (10) days after substantial completion of the Leasehold
Improvements in the Premises, delivery to Landlord of a certificate of occupancy
for the Premises and first occupancy by Tenant of at least 30,000 rentable
square feet of the Premises, Landlord shall reimburse Tenant (or, at Tenant's
election made by notice to Landlord, shall pay directly to Tenant's contractor)
for Tenant's costs and expenses of the Leasehold Improvements in the Premises
(as evidenced by invoices and other supporting documentation reasonably
acceptable to Landlord), up to a




                                      -62-
<PAGE>   63
maximum (when combined with the portion of the allowance disbursed under clause
(a) above) of $450,000.

      Landlord shall have no obligation to disburse any portion of the allowance
not claimed by Tenant within eighteen (18) months after the date hereof.

11.4  LANDLORD'S RIGHT TO TERMINATE LEASE PRIOR TO COMMENCEMENT DATE.

      If during the period between the date of execution of this Lease and the
Commencement Date, Tenant shall fail to comply with any requirements of this
Article XI, and if such failure shall continue for more than ten (10) days after
written notice from Landlord specifying the failure and if within said ten (10)
day period Tenant has not commenced diligently to correct the failure, then
Landlord may, at its option, cancel and terminate this Lease on the date stated
in said notice. Upon such cancellation neither party shall have any continuing
liability to the other hereunder except that Tenant shall repay to Landlord
immediately upon demand by Landlord therefor all payments made by Landlord to
Tenant, if any, as part of the tenant allowance and each party shall remain
responsible according to the terms and provisions of the Lease for its acts or
neglects occurring prior to such cancellation.



                                   ARTICLE XII

                              RIGHT OF FIRST OFFER

12.1  RIGHT OF FIRST OFFER.

      Landlord hereby grants to Tenant a right of first offer to lease (the
"Offer Right") space on the fifth (5th) floor of Office Component (the "Offer
Space") if such




                                      -63-
<PAGE>   64
Offer Space becomes available for occupancy before the fourth (4th) anniversary
of the Commencement Date (or before the end of the initial Term, in the event
Tenant has validly exercised its extension option under Section 2.3). The term
of any lease of Offer Space leased pursuant to this Section shall end on the
last day of the Term of this Lease; provided, that if less than three (3) years
remain in the Term from the date the Offer Space is to be delivered to Tenant,
the Term shall be extended automatically to the date that is three (3) years
after the date of such delivery, and the Annual Base Rent applicable to the
original Premises during the portion of such extended Term after the Term
Expiration Date shall be at a rate equal to the greater of (a) the Annual Base
Rent in effect at the end of the Term or (b) the rate set forth in the Proposed
Terms (defined below).

      If Landlord desires to lease the Offer Space, Landlord shall first send
Tenant notice of the specific terms and conditions, including, without
limitation, the applicable annual base rent and the length of term, upon which
Landlord desires to lease such Offer Space (the "Proposed Terms".) Tenant shall
have five (5) business days subsequent to receipt by Tenant of such notice from
Landlord (the "Offer Date") in which to exercise its option to lease the Offer
Space on the Proposed Terms.

      Within five (5) business days after the Offer Date, Tenant shall by notice
to Landlord accept or reject the offer on the Proposed Terms (failure of Tenant
to respond within such five business day period shall be deemed a rejection of
the offer). In the event Tenant does not accept the offer on the Proposed Terms,
Landlord shall be free for a period up to six (6) months to lease such Offer
Space to



                                      -64-
<PAGE>   65
any third party on substantially the same terms and conditions as set forth in
the Proposed Terms; provided, however, that Landlord shall be entitled to
include in any lease to any such third party, in addition to the Proposed Terms,
commercially reasonable provisions relating to allowances for tenant
improvements. In the event Landlord has not within such six-month period signed
a commitment to lease the applicable Offer Space to a third party on
substantially the same terms and conditions as are contained in the Proposed
Terms, Tenant's rights under this Section shall again be effective with respect
to such Offer Space. Notwithstanding the foregoing, Tenant's right to accept any
offer hereunder and to lease any Offer Space is subject to the additional
conditions precedent that at the time Tenant exercises its right to lease any
such Offer Space and at the time the lease for any such Offer Space commences
(i) Tenant shall not be in default under this Lease beyond applicable grace or
cure periods, and (ii) Tenant shah not have sublet any portion of the Premises
or assigned this Lease pursuant to Section 6.1.6 hereof.

      The rights of Tenant under this Section are expressly subordinate to, and
shall not apply to any extension, expansion or first offer or first refusal
rights granted to other tenants of the Office Component prior to the date
hereof. The rights of Tenant set forth in this Section shall not be binding upon
any institution or mortgagee which acquires title to the Building or any portion
thereof through foreclosure by sale or deed in lieu thereof, or to anyone
claiming by, through or under such institution or mortgagee.



                                      -65-
<PAGE>   66
      Any person dealing with the Offer Space may, without further inquiry, rely
upon a representation in a certificate of Landlord or its successor in title as
to whether or not the provisions of this Section have been satisfied. Time is of
the essence with respect to this Section.

      EXECUTED as a sealed instrument in two or more counterparts on the day and
year first above written.


                                  LANDLORD:

                                  TRUSTEES OF KSA REALTY TRUST


                                  By: /s/ ??????? ??????????
                                      ------------------------------------------
                                                        , as Trustee
                                      of KSA Realty Trust and for
                                      Co-Trustees, but not individually


                                  By: /s/ J. William Richardson
                                      ------------------------------------------
                                      J. William Richardson, as Trustee
                                      of KSA Realty Trust and for
                                      Co-Trustees, but not individually



                                  TENANT:

                                  CAMBRIDGE ENERGY RESEARCH
                                  ASSOCIATES LIMITED PARTNERSHIP


                                  By: CAMBRIDGE ENERGY RESEARCH ASSOCIATES, INC.
                                      ------------------------------------------
                                      General Partner


                                  By: /s/ Daniel H. Lucking, Jr.
                                      ------------------------------------------
                                      Name: Daniel H. Lucking, Jr.
                                      Title: Chief Financial Officer



                                      -66-
<PAGE>   67
CHARLES SQUARE
SITE PLAN















                             [SITE PLAN GRAPHIC]












                                    EXHIBIT A


<PAGE>   68
                                   EXHIBIT A-1



      Three parcels of land in Cambridge, Middlesex County, Massachusetts, shown
as Lots A, C and D on a plan entitled: "Plan of Property owned by The Trustees
of KSA Realty Trust, University Road and Bennett Street, Cambridge,
Massachusetts", prepared by Cullinan Engineering Co., Inc., dated May 6, 1983
and recorded with Middlesex South Registry of Deeds on July 8, 1983, as Plan 
No. 749 (the "Subdivision Plan"), said Lots A, C and D together bounded and
described as follows:

NORTHEASTERLY     by Bennett Street by two lines, measuring respectively 17.20
                  feet and 340.67 feet;

SOUTHEASTERLY     by land now or formerly of the Metropolitan District
                  Commission as shown on the Subdivision Plan, by two lines,
                  measuring respectively, 11.05 feet and 336.17 feet;

SOUTHWESTERLY     by Lot B as shown on the Subdivision Plan, 376.77 feet;


SOUTHERLY         again by said Lot B, by two lines measuring 37.96 feet and
                  4.98 feet; and

NORTHWESTERLY     by University Road, 327.29 feet.

Said Lots A, C and D together contain 127,507 square feet, more or less, 
according to the Subdivision Plan.

      Together with the benefit of a Declaration of Covenants, Easements and
Restrictions dated June 30, 1983, and recorded with said Deeds in Book 15104,
Page 94, as affected by an Amendment to Declaration of Covenants, Easements,
Restrictions and Approval of As-Built Plans dated January 16, 1985, and recorded
with said Deeds in Book 16002, Page 60, together with Plan No. 146 and by an
Approval and Amendment of As-Built Plans Pursuant to Declaration of Covenants,
Easements and Restrictions dated July 9, 1985, and recorded with said Deeds in
Book 16279, Page 524, together with Plan No. 882.

      Together with the benefit of the provisions of a Quitclaim Deed from the
Commonwealth of Massachusetts to Richard L. Friedman et al, Trustees of KSA
Realty Trust dated June 14, 1982 and recorded with said Deeds in Book 14635,
Page 550, the provisions of which are incorporated herein by this reference, as
affected by a Certificate of Completion recorded with said Deeds in Book 16002,
Page 72 and by a Final Certificate of Completion recorded with said Deeds in
Book 16352, Page 349.

      Together with the benefit of a Grant of Electric Service Easement from
Trustees of KSA Realty Trust to Cambridge Electric Light Company dated June 30,
1983 and recorded with said Deeds on July 8 1983 in Book 15104, Page 89.


<PAGE>   69
                                  EXHIBIT A-2                         Level 6





                             [LEVEL 6 FLOOR PLAN]



<PAGE>   70
                                  EXHIBIT A-2                         Level 7



                             [LEVEL 7 FLOOR PLAN]



<PAGE>   71
                                  EXHIBIT A-2                         Level 8




                             [LEVEL 8 FLOOR PLAN]



<PAGE>   72
                                    EXHIBIT B

                               LANDLORD'S SERVICES

I.    CLEANING

      A.   General

           1.   All cleaning work will be performed between 8 a.m. and 12
                midnight, Monday through Friday, unless otherwise necessary for
                stripping, waxing, etc.

           2.   Abnormal waste removal (e.g., computer installation paper, bulk
                packaging, wood or cardboard crates, refuse from cafeteria
                operation, etc.) shall be Tenant's responsibility.

      B.   Daily Operations (5 times per week)

           1.   Tenant Areas

                a.   Empty and clean all waste receptacles; wash receptacles as
                     necessary.

                b.   Vacuum all rugs and carpeted areas.

                c.   Empty, damp-wipe and dry all ashtrays.

           2.   Lavatories

                a.   Sweep and wash floors with disinfectant.

                b.   Wash both sides of toilet seats with disinfectant.

                c.   Wash all mirrors, basins, bowls and urinals.

                d.   Spot clean toilet partitions.

                e.   Empty and disinfect sanitary napkin disposal receptacles.

                f.   Refill toilet tissue, napkin dispensers towel, soap and
                     sanitary napkin dispensers.



                                      B-1
<PAGE>   73
           3. Public Areas

                a.   Wipe down entrance doors and clean glass (interior and
                     exterior).

                b.   Vacuum elevator and hallway carpets and wipe down doors and
                     walls.

                c.   Clean water coolers.

      C.   Operations as Needed (but not less than every other day)

           1.   Tenant and Public Areas.

                a.   Buff all resilient floor areas.

      D.   Weekly Operations

           1.   Tenant Areas, Lavatories, Public Areas

                A.   Hand-dust and wipe clean all horizontal surfaces with
                     treated cloths to include furniture, office equipment,
                     windowsills, ledges, chair rails, baseboards, convector
                     tops, etc., within normal reach.

                b.   Remove finger marks from private entrance doors, light
                     switches and doorways.

                c.   Sweep all stairways.

      E.   Monthly Operation

           1.   Tenant and Public Areas

                a.   Thoroughly vacuum seat cushions on chairs, sofas, etc.

                b.   Vacuum and dust grillwork.

           2.   Lavatories

                a.   Wash down interior walls and toilet partitions.



                                      B-2
<PAGE>   74
      F.   As Required and, Weather Permitting (but no less than once per year)

           1.   Entire Building

                a.   Clean inside of all windows.

                b.   Clean outside of all windows.

      G.   Yearly

           1.   Tenant and Public Areas

                a.   Strip and wax all resilient tile floor areas.

II    HEATING, VENTILATING AND AIR CONDITIONING

      1.   Heating, ventilating and air conditioning as required to provide
           reasonably comfortable temperatures for normal business day occupancy
           (excepting holidays); Monday through Friday from 8:00 a.m. to 6:00
           p.m. and Saturday from 8:00 a.m. to 1:00 p.m. Heating, ventilating
           and air conditioning to be available to Tenant in Tenant's Space 24
           hours per day. Common Area lighting to be provided 24 hours per day.

      2.   Maintenance of any additional or special heating, ventilating and air
           conditioning equipment and the associated operating cost will be at
           Tenant's expense.

III.  WATER

      Hot water for lavatory purposes and cold water for drinking, lavatory and
      toilet purposes.

IV.   ELEVATORS

      Elevators for the use of all tenants and the general public for access to
      and from all floors of the Building. Programming of elevators (including,
      but not limited to, service elevators) shall be as Landlord from time to
      time determines best for the Building as a whole.




                                      B-3
<PAGE>   75

V.    RELAMPING OF LIGHT FIXTURES

      Tenant will reimburse Landlord for the cost of lamps, ballasts and
      starters and the cost of replacing same within the Premises.

VI.   CAFETERIA AND VENDING INSTALLATIONS

           1.   Any space to be used primarily for lunchroom or cafeteria
                operation shall be Tenant's responsibility to keep clean and
                sanitary, it being understood that Landlord's approval of such
                use must be first obtained in writing.

           2.   Vending machines or refreshment service installations by Tenant
                must be approved by Landlord in writing and shall be restricted
                in use to employees and business callers. All cleaning
                necessitated by such installations shall be at Tenant's expense.

VII.  ELECTRICITY

      A.   Landlord, at Landlord's expense, shall furnish electrical energy
           required for heating, ventilating and air conditioning used in or for
           the benefit of Tenant's Space, in accordance with the provisions of
           the Lease of which this Exhibit is a part.

      B.   Tenant shall pay to Landlord for all electrical energy used in or for
           the benefit of Tenant's Space. Tenant initially shall pay an amount
           equal to 1/12th of the Annual Estimated Cost of Electrical Service to
           Tenant's Space in equal installments in advance on the first day of
           each calendar month included in the term.

      C.   Landlord shall have the right to meter Tenant's actual consumption of
           electrical energy. Landlord, may adjust the Estimated Cost of
           Electrical Service to Tenant's Space to reflect Tenant's actual
           consumption of electrical energy. Such adjustment may be made no
           sooner than twelve months from the Commencement Date and no more
           frequently than once every twelve months thereafter.

      D.   Tenant's use of electrical energy in Tenant's Space shall not at any
           time exceed the capacity of any of the electrical conductors or
           equipment in or otherwise



                                      B-4
<PAGE>   76
           serving Tenant's Space. In order to insure that such capacity is not
           exceeded and to avert possible adverse effect upon the Building
           electric service, Tenant shall not, without prior written notice to
           Landlord in each instance, connect to the Building electric
           distribution system any fixtures, appliances or equipment which
           operate on a voltage in excess of 120 volts nominal or make any
           alteration or addition to the electric system of Tenant's Space.
           Unless Landlord shall reasonably object to the connection of any such
           fixtures, appliances or equipment, all additional risers or other
           equipment required therefor shall be provided by Landlord, and the
           cost thereof shall be paid by Tenant upon Landlord's demand. In the
           event of any such connection, Tenant agrees to an increase in the
           Estimated Cost of Electrical Service to Tenant's Space by an amount
           which will reflect the cost to Landlord of the additional service to
           be furnished by Landlord, such increase to be effective as of the
           date of any such connection. If Landlord and Tenant cannot agree
           thereon, such amount shall be conclusively determined by a reputable
           independent electrical engineer or consulting firm to be selected by
           Landlord and paid equally by both parties.

      E.   If at any time after the date of this Lease, the rates at which
           Landlord purchases electrical energy from the public utility
           supplying electrical service to the Building, or any charges incurred
           or taxes payable by Landlord in connection therewith, shall be
           increased or decreased, the Estimated Cost of Electrical Service to
           Tenant's Space shall be increased or decreased, as the case may be,
           by an amount equal to the estimated increase or decrease, as the case
           may be, in Landlord's cost of furnishing the electricity referred to
           above as a result of such increase or decrease in rates, charges or
           taxes. If Landlord and Tenant cannot agree thereon, such amounts
           shall be conclusively determined by a reputable independent
           electrical engineer or consulting firm to be selected by Landlord and
           paid equally by both parties. Any such increase or decrease shall be
           effective as of the date of the increase or decrease in such rate,
           charges or taxes.

      F.   Landlord may, at any time, elect to discontinue the furnishing of
           electrical energy. In the event of any such election by Landlord: (1)
           Landlord agrees to give reasonable advance notice of any such
           discontinuance to




                                      B-5
<PAGE>   77
           Tenant; (2) Landlord agrees to permit Tenant to receive electrical
           service directly from the public utility supplying service to the
           Building and to permit the existing feeders, risers, wiring and other
           electrical facilities serving Tenant's Space to be used by Tenant
           and/or such public utility for such purpose to the extent they are
           suitable and safely capable; (3) Landlord agrees to pay such charges
           and costs, if any, as such public utility may impose in connection
           with installation of Tenant's meters and to make or, at such public
           utility's election, to pay for such other installations as such
           public utility may require, as a condition of providing comparable
           electrical service to Tenant; (4) Tenant shall no longer be required
           to pay the Estimated Cost of Electrical Service to Tenant's Space
           then in effect; (5) Tenant shall thereafter pay, directly to the
           utility furnishing the same, all charges for electrical services to
           the Premises; and (6) electrical service to Tenant's Space shall not
           be discontinued as a result of Landlord's election to discontinue the
           furnishing of electrical energy.







                                      B-6
<PAGE>   78
                                    EXHIBIT C

                              RULES AND REGULATIONS




A.    The following rules and regulations have been formulated for the salary
      and well-being of all tenants of the Building and to insure compliance
      with all municipal, insurance and other requirements. Strict adherence to
      these rules and regulations is necessary to guarantee that each and every
      tenant will enjoy a safe and unannoyed occupancy in the Building in
      accordance with its Lease. Any continuing violation of these rules and
      regulations by Tenant, after notice from Landlord, shall be deemed to be
      an Event of Default under its lease.

B.    Landlord may, upon request by any tenant, waive compliance by such Tenant
      to any of these rules and regulations, provided that (1) no waiver shall
      be effective unless signed by Landlord or Landlord's authorized agent, (2)
      any such waiver shall not relieve such tenant from the obligation to
      comply with such rule or regulation in the future unless expressly
      consented to by Landlord, (3) no waiver granted to any tenant shall
      relieve any other tenant from the obligation of complying with the rules
      and regulations unless such other tenant has received a similar waiver in
      writing from the Landlord, and (4) any such waiver by Landlord shall not
      relieve Tenant from any obligation or liability of Tenant to Landlord
      pursuant to the Lease for any loss or damage occasioned as a result of
      Tenant's failure to comply with any such rule or regulation.

                                 --------------

1.    The sidewalks, entrances, passages, courts, elevators, vestibules,
      stairways, corridors, halls or other parts of the Building not occupied by
      any tenant shall not be obstructed or encumbered by any tenant or used for
      any purpose other than ingress and egress to and from the Leased Space. If
      the Leased Space is situated on the ground floor of the Building, the
      tenant thereof shall, at such tenant's own expense, keep the sidewalks and
      curb directly in front of the premises clean and free from ice, snow and
      debris. Landlord shall have the right to control and operate the public
      portions of the Building and the facilities furnished for common use of
      the tenants in such manner as Landlord deems best for the




                                      -1-
<PAGE>   79
      benefit of the tenants generally. No tenant shall permit the visit to the
      Premises of persons in such numbers or under such conditions as to
      interfere with the use and enjoyment by other tenants of the entrances,
      corridors, elevators and other public portions or facilities of the
      Building. 

2.    No awnings or other projections shall be attached to the outside walls of
      the Building without the prior written consent of Landlord. No drapes,
      blinds, shades, or screens shall be attached to or hung in, or used in
      connection with, any window or door of the Premises, without the prior
      written consent of Landlord. Such awnings, projections, curtains, blinds,
      shades, screens or other fixtures must be of a quality, type, design and
      color, and attached in the manner, approved by Landlord. Tenant shall not
      hang or shake anything out of any window or open any window at its Leased
      Space or in the common area of the Building outside.

3.    No showcases or other articles shall be put outside, in front of or
      affixed to any part of the exterior of the Building, nor placed in the
      halls, corridors or vestibules without the prior written consent of
      Landlord. Tenant shall have right to place patio furniture on leased deck
      area with prior Landlord architectural approval.

4.    The water, toilets and wash closets and other plumbing fixtures shall not
      be used for any purposes other than those for which they were constructed,
      and no sweepings, rubbish, rags, chemicals, paints, cleaning fluids or
      other substances shall be thrown therein. All damages resulting from any
      misuse of the fixtures shall be borne by the Tenant who, or whose
      servants, employees, agents, visitors or licensees, shall have caused the
      same.

5.    There shall be no marking, painting, drilling into or in any way defacing
      the Building or any part of the Leased Space visible from public areas of
      the Building. Tenant shall not construct, maintain, use or operate within
      the Leased Space any electrical device, wiring or apparatus in connection
      with a loud speaker system or other sound system, except as reasonably
      required for its communication system and approved prior to the
      installation thereof by Landlord. No such loud speaker or sound system
      shall be constructed, maintained, used or operated outside of the Leased
      Space.

6.    No bicycles, vehicles or animals, birds or pets of any kind shall be
      brought into or kept in or about the Leased Space, and no cooking (except
      for hot-plate cooking and microwave



                                      -2-
<PAGE>   80
      cooking by Tenant's employees for their own consumption, the equipment for
      and location of which are first approved by Landlord) shall be done or
      permitted by any tenant on the Leased Space. No tenant shall cause or
      permit any unusual or objectionable odors to be produced upon or permeate
      from the Leased Space.

7.    No space in the Building shall be used for manufacturing of goods for sale
      in the ordinary course of business, for the storage in bulk of merchandise
      or for the sale at auction of merchandise, goods or property of any kind.
      Furthermore, the use of the Leased Space by each tenant was approved by
      Landlord prior to execution of the Lease and such use may not be changed
      without the prior written approval of Landlord.

8.    No tenant shall make any unseemly or disturbing noises or disturb or
      interfere with occupants of the Building or neighboring buildings or
      premises or those having business with them whether by the use of any
      musical instrument, radio, talking machine, unmusical noise, whistling,
      singing or in any other way. No tenant shall throw anything out of the
      doors or windows or down the corridors or stairs.

9.    No flammable, combustible, radioactive, infectious, or explosive fluid
      chemical or substance shall be brought or kept upon the Leased Space.

10.   No additional locks or bolts of any kind shall be placed upon any of the
      doors or windows by any tenant, nor shall any changes be made in existing
      locks or the mechanism thereof. The Tenant shall, and shall cause its
      employees to, lock the doors to the Leased Space as it and they leave at
      the end of each working day and, if after ordinary business hours,
      ascertain that the doors of the Building by which it and they leave are
      locked securely. Each tenant shall, upon the termination of its tenancy,
      restore to the Landlord all keys of stores, offices, storage and toilet
      rooms either furnished to, or otherwise procured by, such tenant, and in
      the event of the loss of any keys so furnished, such tenant shall pay to
      Landlord the cost thereof.

11.   Landlord reserves the right to inspect all freight to be brought into the
      Building and to exclude from the Building all freight which violates any
      of these rules and regulations of the Lease.



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12.   No tenant shall pay any employees on the Premises, except those actually
      working for such tenant on the Premises.

13.   Landlord reserves the right to exclude from the Building at all times any
      person who is not known or does not give proper and satisfactory
      identification to the Building management, security guard on duty or
      security system monitor. Landlord may, at its option, require all persons
      admitted to or leaving the Building between the hours of 6:00 p.m. and
      8:00 a.m. on Monday through Friday, and at any hour on Saturdays, Sundays
      and legal holidays, to register. Each tenant shall be responsible for all
      persons for whom it authorizes entry into or exit out of the Building, and
      shall be liable to Landlord for all acts or omissions of such persons. The
      foregoing rule does not apply to routine retail customers of retail
      tenants during customary business hours.

14.   The Leased Space shall not, at any time, be used for lodging or sleeping
      or for any immoral or illegal purpose.

15.   Each tenant, before closing and leaving its premises at any time, shall
      see that all windows are closed and all lights turned off.

16.   Landlord's employees shall not perform any work or do anything outside of
      their regular duties, unless under special instruction from the management
      of the Building. The requirements of tenants will be attended to only upon
      application to Landlord and any such special requirements shall be billed
      to Tenant (and paid with the next installment of rent due) at the schedule
      of charges maintained by Landlord from time to time or at such charge as
      is agreed upon in advance by Landlord and Tenant.

17.   Canvassing, soliciting and peddling in the Building is prohibited and each
      tenant shall cooperate to prevent the same.

18.   There shall not be any hand trucks used in any leased space, or in the
      public halls of the Building, either by any tenant or by jobbers or
      others, in the delivery or receipt of merchandise, except those equipped
      with rubber tires and side guards. Tenant shall be responsible to Landlord
      for any loss or damage resulting from any deliveries of Tenant to the
      Building.




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19.   Mats, trash or other objects shall not be placed in the public corridors.

20.   No one except Landlord and its employees and agents shall be allowed on
      the roof of the Building or any basement areas except those leased to a
      tenant or otherwise designated for tenant use.

21.   No tenant shall place any sign or advertising notice in any part of the
      Building except as approved by Landlord, or use any advertising or take
      any other action which in Landlord's judgment might tend to affect
      adversely the reputation of the Building and its desirability as a
      building for retail stores and offices.








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