Registration of inherited property in name of four sons

I need your advice on Inherited property @ Delhi We have property in Delhi purchased by my Grandfather 50 years back but that time no paper work. he died in 1970's & had five sons & three daughters, one son at the time of birth adopted by brother in law of my GF. In 90's four sons who lived in that property had probate through court for administered that property also by taking NOC from that one son & three sisters. but further no paper work was made like registry etc. in the name of four sons. I think that probate papers not valid now. We wants to sell that property by four brothers & divide the amt equally, but before that we requires registry. please let me know how to do registry & what papers requires ? how much time taken to complete registry? Can registry be done based on that probate ? or what is the procedure ? as I know we not required to take NOC from ( only one sister alive ) as she has no right as per Hindu Succession act .