Please recall a serious discussion some time back on this forum as to the validity of a sale agreement signed only by the vendor. I would like to bring to your notice a recent Supreme Court judgement on this aspect, reported in (2009) 2 SCC 582, Aloka Bose v. Parmatma Devi and others.
The Supreme Court held "In India, an agreement of sale signed by the vendor alone and delivered tot he purchaser, and accepted by the purchaser, has always been considered to be a valid contract. In the event of breach by vendor, it can be specifically enforced by the purchaser." (Para 18)