What are the documents to be verified before owning a flat?

There are about 12 documents that one must be assured of before buying a house/flat. Sale deed, mother deed (parent document to trace original ownership), encumberance certificate, building approval plan, Khata certificate, Power of Attorney, commencement certificate (in case of under construction property), conversion certificate (agriculture to non-agriculture land), betterment charges receipt, latest tax paid receipt, completion certificate and occupancy certificate.