I have 4 acres of agricultural land. In 2008 i have made a sale agreement(not on stamp paper) to a party for 17 lakhs and agreed to receive an 8 lakhs as advance. I received 5 lakhs as advance and remaining 3 lakhs was agreed to be paid in cash and cheque pertaining to same amount is gieeven dating the date on which amount 3 lakh amount is given.But the purchaser had not given me remaining advance amount with in the time mentioned, and i denied to make a stamped agreement.In the sale agreement done when i received 5 lakhs advance no time frame was mentioned as to when registartion would be done.Now after 4 years the purchaser had sent a legal notice stating me to sell the land at the same price for which agreement was done.Does the agreements which are not done on stamp papers valued? And what happns if i proceed to sell my land to another party ignoring the notice?