This section is from the book "The Law Of Contracts", by William Herbert Page. Also available from Amazon: Commercial Contracts: A Practical Guide to Deals, Contracts, Agreements and Promises.
Either partner may at any time sell bis interest in said partnership, provided, however, that he shall first, in writing, offer the same to the other partner for a specified sum or price, and if such offer be not accepted, in writing, within
---------days thereafter, he may then offer the same to any person for the same or a higher sum or price; but no sale thereof shall be made to any third person or persons for any less sum or price, until after the same has been offered, in writing, to the other partner for the same less sum or price, and the offer at such less sum or price shall not have been accepted within---------days thereafter.
See references under Sec. 3776.