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                                                                    EXHIBIT 3.20

                                     BY-LAWS

                                       OF

                                 DP CA CORP INC.

                                    ARTICLE I

                                     OFFICE

         SECTION 1.1 Principal Office. The Corporation shall maintain its
principal office in the Township of Ann Arbor, State of Michigan.

         SECTION 1.2 Registered Office. The Corporation shall maintain a
registered office in the State of Michigan as required by the Michigan Business
Corporation Act (the "Act").

         SECTION 1.3 Other Offices. The Corporation may have such offices within
and without the State of Michigan as the business of the Corporation may require
from time to time. The authority to establish or close such other offices may be
delegated by the Board of Directors to one or more of the Corporation's
officers.

         SECTION 1.4 Place of Meetings. All meetings of the Corporation's
stockholders or Board of Directors shall be held at the Corporation's principal
office or at such place as shall be designated in the notice of such meetings.

                                   ARTICLE II

                                  STOCKHOLDERS

         SECTION 2.1 Annual Meeting of Stockholders. An annual meeting of the
stockholders shall be held in each year, on the 3rd Wednesday of March, or if
such date is a holiday, the meeting shall be on the next succeeding business
day. One of the purposes of the annual meeting of the stockholders shall be to
elect a Board of Directors. If the annual meeting is not held on the date
designated therefor, the Board of Directors shall cause the meeting to be held
thereafter as convenient but within ninety (90) days after said designated date.

         SECTION 2.2 Special Meetings. A special meeting of the stockholders may
be called at any time by the President, or by a majority of the Board of
Directors, or the holders of not less than twenty-five percent (25%) of all the
shares entitled to vote at such special meeting. The method by which such
meeting may be
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called is as follows: Upon receipt of a specification in writing setting forth
the date and purposes of such proposed special meeting, signed by the President,
or by a majority of the Board of Directors, or by stockholders as above
provided, the Secretary of this Corporation shall prepare, sign and mail the
notices requisite to such meeting.

         SECTION 2.3 Notice of Stockholders' Meeting. Not less than ten (10)
days, nor more than sixty (60) days, prior to the date of an annual or special
meeting of stockholders, written notice of the time, place and purposes of such
meeting shall be mailed, as hereinafter provided, to each stockholder entitled
to vote at such meeting. Every notice shall be deemed duly served when the same
has been deposited in the United States mail, or with a private courier service
(such as Federal Express), with postage prepaid, addressed to the stockholder at
the stockholder's address as it appears on the Corporation's records, or if a
stockholder shall have filed with the Secretary of the Corporation a written
request that the notice be sent to some other address, then at such other
address.

         SECTION 2.4 Waiver of Notice. Notice of the time, place and purpose of
any meeting of the stockholders may be waived by telegram, telecopy, confirmed
facsimile or other writing, either before or after such meeting has been held.
The attendance of any stockholder at any stockholders' meeting shall constitute
a waiver of any notice to which such stockholder may be entitled pursuant to
these By-Laws, except when the stockholder attends a meeting for the express
purpose of objecting, at the beginning of the meeting, to the transaction of any
business because the meeting is not lawfully convened.

         SECTION 2.5 Quorum of Stockholders. A majority of the outstanding
shares of this Corporation entitled to vote, represented by the record holders
thereof in person or by proxy, shall constitute a quorum at any meeting of the
stockholders. The stockholders present in person or by proxy at such meeting may
continue to do business until adjournment, notwithstanding the withdrawal of
stockholders which results in less than a quorum remaining. Whether or not a
quorum is present, the meeting may be adjourned by a vote of the shares present.

         SECTION 2.6 Record Date for Determination of Stockholders. The Board of
Directors shall fix a record date for determining stockholders entitled to
receive payment of a share dividend or distribution, or allotment of a right,
which date shall not precede the date on which the resolution fixing the record
date is adopted by the Board of Directors. The date shall not be more than 60
days before the payment of the share dividend or distribution or allotment of a
right or other action.

         SECTION 2.7 Transaction of Business. Business transacted at an annual
meeting of stockholders may include all such business as may properly come
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before the meeting. Business transacted at a special meeting of the stockholders
shall be limited to the purposes set forth in the notice of the meeting.

         SECTION 2.8 Voting. Except as otherwise required by the Act or the
Corporation's Articles of Incorporation, each stockholder of the Corporation
shall, at every meeting of the stockholders, be entitled to one vote in person
or by proxy for each share of capital stock of this Corporation held by such
stockholder, subject, however, to the full effect of the limitations imposed by
the fixed record date for determination of stockholders set forth in Section 2.6
of this Article.

         SECTION 2.9 Proxies. No proxy shall be deemed operative unless and
until signed by the stockholder and filed with the Secretary of the Corporation.
All proxies shall be executed by the appointing stockholder or such
stockholder's authorized attorney; provided that no proxy shall be valid for
more than three (3) months after execution of such proxy unless the proxy
specifically provides for a longer period.

         SECTION 2.10 Vote by Stockholder Corporation. Any other corporation
owning shares of this Corporation entitled to vote may vote upon the same by the
president of such stockholder corporation, or by proxy appointed by him, unless
some other person shall be appointed to vote upon such shares by resolution of
the Board of Directors of such stockholder corporation.

         SECTION 2.11 Inspectors of Election. Whenever any person entitled to
vote at a meeting of the stockholders shall request the appointment of
inspectors, the chairman of the meeting shall appoint not more than three
inspectors, who need not be stockholders. If the right of any person to vote at
such meeting shall be challenged, the inspectors shall determine such right. The
inspectors shall receive and count the votes either upon an election or for the
decision of any question, and shall determine the result. Their certificate of
any vote shall be prima facie evidence thereof.

         SECTION 2.12 Action by Written Consent. Any action required or
permitted by the Michigan Business Corporation Act to be taken at an annual or
special meeting of stockholders may be taken without a meeting, without prior
notice and without a vote, if consents in writing, setting forth the action so
taken, are signed by the holders of all of the outstanding shares of the
Corporation entitled to vote.

         SECTION 2.13 Order of Business. The order of business at the annual
meeting of the stockholders, and so far as practicable at all other meetings of
the stockholders, shall be as follows:

         1.   Proof of Notice of the Meeting
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         2.   Determination of a Quorum
         3.   Election of Directors
         4.   Unfinished Business
         5.   New Business
         6.   Adjournment

         Except with respect to a specific rule to the contrary in these By-Laws
or the Act, Robert's Rules of Order shall be used to resolve all to resolve all
procedural disputes that may arise at a stockholder's meeting.

                                   ARTICLE III

                               BOARD OF DIRECTORS

         SECTION 3.1 Authority. The Board of Directors shall have ultimate
authority over the conduct and management of the business and affairs of the
Corporation.

         SECTION 3.2 Number and Term. Except as otherwise provided by the
Corporation's Articles of Incorporation, the number of directors of the
Corporation shall be fixed from time to time by the vote of a majority of the
entire Board; provided, that the number of directors shall not be less than one
nor shall the action of the Board shorten the term of any director at that time
in office.

         SECTION 3.3 Term. Each Director shall hold office from the date of
election and qualification until his or her successor shall have been duly
elected, or until his or her earlier removal, resignation, death or incapacity.

         SECTION 3.4 Removal. Any Director may be removed from office, with or
without cause, by a vote of a majority of the shares of the Corporation's shares
entitled to vote.

         SECTION 3.5 Vacancies. Vacancies in the Board of Directors (including
vacancies resulting from an increase in the number of directors) shall be filled
by appointment made by a majority of the remaining directors. Each person so
appointed shall hold office until the next election of Directors or until his or
her successor shall be elected and qualified.

         SECTION 3.6 Organizational Meeting of Board. At the place of holding
the annual meeting of stockholders, and immediately following the same, the
Board of Directors as constituted upon final adjournment of such annual meeting,
shall convene for the purposes of electing officers, setting the selling price
for the Corporation's shares as provided in Section 3.18 and transacting any
other business properly brought before it, provided that the organizational
meeting in any
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year may be held at a different time and place than that herein provided by
consent of a majority of the Directors of such new Board.

         SECTION 3.7 Regular Meetings of the Board. Regular meetings of the
Board of Directors may be held at times and places agreed upon by a majority of
the directors at any meeting of the Board of Directors and such regular meetings
may be held at such times and places without any further notice of the time,
place or purposes of such regular meetings.

         SECTION 3.8 Special Meetings of the Board. Special meetings of the
Board of Directors may be called at the request of any member of the Board at
any time by means of written notice of the time, place and purpose thereof
mailed to each director not less than one (1) day, nor more than sixty (60)
days, prior to the date fixed for the holding of any special meeting of
Directors, but action taken at any such meeting shall not be invalidated for
want of notice if such notice shall be waived as hereinafter provided.

         SECTION 3.9 Notices. Every notice of a meeting of the Board of
Directors shall be deemed duly served when the same has been deposited in the
United States mail, or with a private courier service (such as Federal Express),
with postage prepaid, addressed to the director at his or her last known
address, or if a director shall have filed with the Secretary of the Corporation
a written request that the notice be sent to some other address, then at such
other address.

         SECTION 3.10 Waiver of Notice. Notice of the time, place and purpose of
any meeting of the Board of Directors may be waived by telegram, telecopy,
confirmed facsimile or other writing, either before or after such meeting has
been held. The attendance of any director at any directors' meeting shall
constitute a waiver of any notice to which such director may be entitled
pursuant to these By-Laws, except when the director attends a meeting for the
express purpose of objecting, at the beginning of the meeting, to the
transaction of any business because the meeting is not lawfully convened.

         SECTION 3.11 Participation by Telecommunications. Any Director may
participate in, and be regarded as present at, any meeting of the Board of
Directors by means of conference telephone or any other means of communication
by which all persons participating in the meeting can hear each other at the
same time.

         SECTION 3.12 Quorum of Directors. A majority of the directors then in
office shall constitute a quorum for transaction of business.

         SECTION 3.13 Action. The Board of Directors shall take action pursuant
to resolutions adopted by the affirmative vote of a majority of the Directors
participating in a meeting at which a quorum is present, or affirmative
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vote of a greater number of Directors where required by the Corporation's
Articles of Incorporation or by law.

         SECTION 3.14 Action by Unanimous Written Consent. Any action required
or permitted to be taken by the Board of Directors of the Corporation may be
taken without a meeting, without prior notice, and without a vote if consents in
writing, setting forth the action so taken, are signed by all of the directors
of the Corporation.

         SECTION 3.15 Selection of Officers. The Board of Directors shall select
a president, treasurer, and a secretary, and may select a chairman of the Board,
one or more vice presidents, one or more assistant treasurers, and one or more
assistant secretaries, and any other officers that the Board of Directors deems
to be in the best interests of the Corporation, which officers may be appointed
and their duties prescribed by resolution of the Board.

         SECTION 3.16 Power to Appoint Other Officers and Agents. The Board of
Directors shall have power to appoint such other officers and agents as the
Board may deem necessary for transaction of the business of the Corporation.

         SECTION 3.17 Removal of Officers and Agents. Any officer or agent may
be removed by the Board of Directors whenever, in the judgment of the Board, the
business interests of the Corporation will be served thereby.

         SECTION 3.18 Share Sale Price. At each organizational meeting of the
Board of Directors, the Board shall set the share selling price for purposes of
various Stock Purchase Agreements entered into from time to time between the
Corporation and its stockholders.

         SECTION 3.19 Delegation of Powers. For any reason deemed sufficient by
the Board of Directors, whether occasioned by absence or otherwise, the Board
may delegate all or any of the powers and duties of any officer to any other
officer or director, but no officer or director shall execute, verify or
acknowledge any instrument in more than one capacity unless specifically
authorized by the Board of Directors.

         SECTION 3.20 Power to Appoint Committees of the Board. The Board of
Directors shall have power to designate, by resolution, committees composed of
one or more directors who, to the extent provided in such resolution, may
exercise the business and affairs of the Corporation except as restricted by
statute. In the absence or disqualification of a member of the committee, the
members thereof present at a meeting and not disqualified from voting, whether
or not they constitute a quorum, may unanimously appoint another director of the
Board to act at the meeting in place of such an absent or disqualified member. A
majority of the
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members of any committee of the Board will constitute a quorum for all committee
action.

         SECTION 3.21 Compensation. The Board of Directors may by resolution
authorize the payment to all Directors of a uniform sum for attendance at each
meeting or a uniform stated fee as a Director. No such payment shall preclude
any Director from serving the Corporation in any other capacity and receiving
compensation therefor. The Board of Directors may also by resolution authorize
the payment of reimbursement of all expenses of each Director related to the
Director's attendance at meetings.

         SECTION 3.22 Order of Business. The order of business at all meetings
of the Board of Directors shall be:

         1.   Determination of a quorum
         2.   Reading and disposal of all unapproved minutes
         3.   Reports of officers and committees
         4.   Unfinished business
         5.   New business
         6.   Adjournment

         Except with respect to a specific rule to the contrary in these By-Laws
or the Act, Robert's Rules of Order shall be used to resolve all procedural
disputes that may arise at a Director's meeting.

                                   ARTICLE IV

                                    OFFICERS

         SECTION 4.1 In General. The officers of the Corporation shall consist
of a chairman, a president, a vice president, a secretary, a treasurer and such
additional vice presidents, assistant secretaries, assistant treasurers, and
other officers and agents as the Board of Directors from time to time deems
advisable. All officers shall be appointed by the Board to serve at its
pleasure. Except as otherwise provided by law or in the Articles of
Incorporation, any officer may be removed by the Board of Directors at any time,
with or without cause. Any vacancy, however occurring, in any office may be
filled by the Board of Directors for the unexpired term. One person may hold two
or more offices. Each officer shall exercise authority and perform the duties
set forth in these By-Laws and any additional authority and duties as the Board
of Directors shall determine from time to time.
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         SECTION 4.2 Chairman of the Board. The Chairman of the Board shall be
selected by and from the membership of the Board of Directors. He shall conduct
all meetings of the Board and shall perform all duties incident thereto.

         SECTION 4.3 President. The President shall have general and active
management of the business of the Corporation and shall see that all orders and
resolutions of the Board are carried into effect. He shall be ex-officio, a
member of all standing committees, and shall have the general powers and duties
of supervision and management usually vested in the office of president of a
corporation.

         SECTION 4.4 Vice Presidents. Each Vice President shall serve under the
direction of the President and shall perform such other duties as the Board of
Directors shall from time to time direct.

         SECTION 4.5 Secretary. Except as otherwise provided by these By-Laws or
otherwise determined by the Board of Directors, the Secretary of the Corporation
shall serve under the direction of the President and shall perform such other
duties as the Board shall from time to time direct. The Secretary shall attend
all meetings of the stockholders and the Board of Directors, and shall preserve
in the books of the Company true minutes of the proceedings of all such
meetings. The Secretary shall safely keep in his or her custody the seal of the
Corporation, and shall have authority to affix the same to all instruments where
its use is required. The Secretary shall give all notices required by statute,
by-law or resolution.

         SECTION 4.6 Treasurer. The Treasurer shall serve under the President
and shall perform such other duties as the Board shall from time to time direct.
The Treasurer shall have custody of all corporate funds and securities, and
shall keep in books belonging to the Corporation full and accurate accounts of
all receipts and disbursements. The Treasurer shall deposit all monies,
securities and other valuable effects in the name of the Corporation in such
depositories as may be designated for that purpose by the Board of Directors and
shall disburse the funds of the Corporation as may be ordered by the Board. The
Treasurer shall upon request report to the Board of Directors on the financial
condition of the Corporation.

         SECTION 4.7 Assistant Secretary and Assistant Treasurer. The Assistant
Secretary, in the absence or disability of the Secretary, shall perform the
duties and exercise the powers of the Secretary. The Assistant Treasurer, in the
absence or disability of the Treasurer, shall perform the duties and exercise
the powers of the Treasurer.
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                                    ARTICLE V

                               STOCK AND TRANSFERS

         SECTION 5.1 Certificates for Shares. Every stockholder shall be
entitled to a certificate of the shares to which he has subscribed, said
certificate to be signed by the Chairman of the Board, President or a Vice
President, and may be sealed with the seal of the Corporation or a facsimile
thereof certifying the number and class of shares; provided, that where such
certificate is signed by a transfer agent or an assistant transfer agent, or by
a transfer clerk acting on behalf of such entity, and by a registrar, the
signature of any such officers may be a facsimile.

         If the shares of the Corporation shall become listed on a national
securities exchange, the Corporation may eliminate certificates representing
such shares and provide such shares and provide for such other methods of
recording, noticing ownership and disclosure as may be provided by the rules of
that national securities exchange.

         SECTION 5.2 Transferable Only on Books of the Corporation. Shares shall
be transferable only on the books of the Corporation by the holder thereof in
person or by an attorney lawfully constituted in writing, and upon surrender of
the certificate therefor. A record shall be made of every such transfer and
issue. Whenever any transfer is made for collateral security and not absolutely,
the fact shall be so expressed in the entry of such transfer.

         SECTION 5.3 Stock Ledger. The Corporation shall maintain a stock ledger
which contains the name and address of each stockholder and the number of shares
of stock of each class which the stockholder holds. The stock ledger may be in
written form or in any other form which can be converted within a reasonable
time into written form for visual inspection. The original or a duplicate of the
stock ledger shall be kept at the office of a transfer agent for the particular
class of stock, within or without the State of Michigan, or, if none, at the
principal office of the Corporation in the State of Michigan.

         SECTION 5.4 Registered Stockholders. The Corporation shall have the
right to treat the registered holder of any share as the absolute owner thereof,
and shall not be bound to recognize any equitable or other claim to or interest
in such share on the part of any other person, whether or not the Corporation
shall have express or other notice thereof, save as may be otherwise provided by
the laws of Michigan.

         SECTION 5.5 Cancellation; Missing Certificates. All certificates
surrendered to the Corporation for transfer shall be cancelled and no new
certificates representing the same number of shares shall be issued until the
former
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certificate or certificates for the same number of shares shall have been so
surrendered and cancelled. In the event that a certificate of stock is lost or
destroyed another may be issued and unless waived by the President, the party
alleging loss or destruction of the certificate shall post a bond or agree to
indemnify the Corporation, at the election of the President, in an amount not
exceeding two (2) times the value of the stock.

                                   ARTICLE VI

                                   INSTRUMENTS

         SECTION 6.1 Checks, Etc. All checks, drafts and orders for payment of
money shall be signed in the name of the Corporation or any assumed name under
which the Corporation has duly filed a certificate therefor and shall be
countersigned by such officers or agents as the Board of Directors shall from
time to time designate for that purpose.

         SECTION 6.2 Contracts, Conveyances, Etc. When the execution of any
contract, conveyance or other instrument has been authorized without
specification of the executing officers, the president or any vice president, or
the treasurer or assistant treasurer, or the secretary or assistant secretary,
may execute the same in the name and on behalf of this Corporation, and may
affix the corporate seal thereto. The Board of Directors shall have power to
designate the officers and agents who shall have authority to execute any
instrument on behalf of this Corporation.

         SECTION 6.3 Voting Shares of Other Corporations. Stock of other
corporations or associations, registered in the name of the Corporation, may be
voted by the President, a Vice President or a proxy appointed by either of them.
The Board of Directors may by resolution appoint some other person to vote the
shares.

                                   ARTICLE VII

                              AMENDMENT OF BY-LAWS

         SECTION 7.1 Amendment. These By-Laws may be amended, altered, changed,
added to or repealed by the affirmative vote of a majority of the shares
entitled to vote at any regular or special meeting of the stockholders if notice
of the proposed amendment, alteration, change, addition or repeal be contained
on the notice of the meeting, or by the affirmative vote of the majority of the
Board of Directors if notice of the proposed amendment, alteration, change,
addition or repeal be contained in the notice of the meeting or is given at the
meeting preceding the meeting at which the change is adopted, provided, however,
that no change of the date for the annual meeting of the stockholders shall be
made within thirty (30) days next before the day on which such meeting is to be
held unless consented to in writing, or by a resolution adopted at a meeting, by
a majority of all stockholders entitled to vote at the annual meeting.