we had executed agreement to sell for purchase of a two bhk flat in pune way back in 2000 . builder has given us the posssesion letter after receipt of full payment. however no final sale deed was done . flat is in a building having 30falts which is managed by housing co op society and hsg co op society has obtained deemed conveyance also for the building . pl let us know whether we need to have final sale deed from the builder and if he is no longer in the business what to do . our names are figuring in the deemed conyeyance deed obtained by the society . pl advice whether thsi is sufficient for us to prove the owenership of our flat and for selling the same.