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                                                                    EXHIBIT 10TT




                               [LOGO] INTELLICORP
                            1975 EL CAMINO REAL WEST
                          MOUNTAIN VIEW, CA 94040-2216



                                                                  March 30, 1999



To Investor


Re:         PURCHASE AND SALE OF COMMON STOCK


Dear XXX:


        This letter documents our agreement regarding the purchase and sale of
shares of Common Stock of IntelliCorp, Inc. (the "Company"). When signed by you
it will constitute a binding agreement between us for the period of one year
from March 30, 1999 until March 30, 2000 (the "Demand Period"). The Company
shall have the right to sell to you (and to require you to purchase) shares of
Company Common Stock, on the terms set forth below, which right shall terminate
on expiration of the Demand Period.

        This will confirm that the Company is entitled to sell, and you will
purchase, during the Demand Period, up to a total of $XXX ("Investment Maximum")
in value of Common Stock of the Company in one or more separate transactions
("Investment"). This agreement, in conjunction with like agreements separately
executed effective March 30, 1999 with Delaware State Employees' Retirement
Fund, Declaration of Trust for Defined Benefit Plans of Zeneca Holdings Inc.,
and Declaration of Trust for Defined Benefit Plans of ICI American Holdings
Inc., represent an aggregate maximum financing of $3,000,000 (collectively
called the "Financing").

        For your convenience, when the Company decides to exercise its right
under this agreement, the Company will first attempt to arrive at a mutually
agreeable ratio of Investment between you and the other parties in this
financing. If no agreement can be reached between you, the Company has the right
to demand an Investment mix based on the proportional share of each party's
Investment Maximum compared to the aggregate combined maximum of $3,000,000 in
this Financing.



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Purchase and Sale of Common Stock
March 30, 1999
Page 2



        When the Company determines that it wishes to sell shares, it will
provide you written notice ("notice date") of its election to exercise its right
under this agreement; the notice shall specify the dollar amount of the shares
to be sold by the Company and purchased by you and the purchase date, which
shall be not more than ten (10) business days after such notice. The purchase
price for any shares purchased by you hereunder shall be equal to $1.50 per
share or 10% above market price (where market price is as defined below),
whichever is greater, up to a maximum price of $3.00 per share. However, if
during the term of this agreement, the Company sells and issues additional
shares of common stock (excluding issuances on exercise of employee or director
stock options or issuance of shares under this agreement or like agreements with
the parties to this Financing) at a price per share less than the purchase price
per share under this agreement, the purchase price for such shares sold to you
shall be adjusted in the same manner as the conversion price is adjusted in the
Company's Convertible Note dated April 19, 1996 (Section 3), and following any
such adjustment, additional common stock shares will be issued to you by the
Company to reflect this adjustment of the purchase price.

        Market price is defined as the average closing price over the five (5)
trading days ending the day prior to the notice date. On the purchase date (or
as soon thereafter as practically possible), you will deliver cash in
immediately available funds in the amount of the purchase price of such shares.
Within five (5) days after the receipt of funds, the Company will deliver to you
a certificate representing the number of shares being purchased by you.

        This letter will also confirm your investment intent with respect to the
purchase and sale of the shares thereunder. You agree and acknowledge that you
are purchasing the shares for your own account, not with a view to resell them,
and that the certificates for any shares will bear restrictive legends to that
effect. Such shares shall also be subject to registration rights in your favor
which will require the Company to file with the SEC an S-3 Registration
Statement (or equivalent) covering your resale of such shares within 3 months
after the end of the demand period, or within 3 months of the last transaction
purchase date, if earlier.




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Purchase and Sale of Common Stock
March 30, 1999
Page 3



            If the foregoing accurately describes our agreement regarding the
purchase and sale of the Shares, please so indicate by signing and returning
this letter to me.





                                             Sincerely,

                                             INTELLICORP, INC.



                                             By:________________________________
                                             Kenneth A. Czaja
                                             Chief Financial Officer

THE FOREGOING IS HEREBY
AGREED TO AND ACCEPTED:

XXXX.



By:_________________________________