Mrs. Harriss wrote to D stating that she intended to dispose of her stock and leases and that before disposition, she would sell to D at a substantial discount. That offer was refused by D. Mr. Harriss then formed P, and then Mrs. Harris then sold P her 777 shares of stock and all rights in three property leases. D refused to recognize the transfer of stock and refused to accept checks tendered in payment of monthly assessments. D asserted that Mrs. Harriss failed to comply with the restrictions on the sale of the stock referred to in the endorsement on the stock certificate. P and Mrs. Harriss contend that these restrictions are invalid and unenforceable as a restraint on alienation.