Property Bought on Sale Agreement & General Power of Attorney

An independent house in Faridabad district was purchased by my father in the Year 1995 (Around 25 years ago). But the house was bought on Sale Agreement & General power of Attorney. Sale agreement is in my Mother's name and GPA was transferred by previous owner in my Father's name. Now its been around 25 years and my father is no more. We need to get the house registered now so we can sale it further. Please advice how can we do that and what is the procedure. We can't connect with the previous owner its been 25 years and we have now idea about their availability and can't track them in any case. Since the GPA is in my father's name how can this be further transferred either to me or to my mother's name and than how can we get the house registered. We are living in the same property since 25 years without any dispute from anyone. In government records the house owner name is still showing as previous owner, since it was bought on GPA. Basically we now want to get the house registered so we can be the owner of the house in government records and than further sell it. We will not be able to sell it with GPA. Kindly help us with the solution.