I have paid a token advance of Rs 50000 on 24-04-2007 for purchase of a land. It was agreed that the total payment would be cleared in three months from the date. On 28-07-2007 additional amount of Rs. 600000 was paid and an agreement of sale was entered on 28-04-2007. The stamp papers were purchased on 28-04-2007 and the date was written as 24-04-2007. Is the agreement valid. The value of stamp papers used also 3 papers of is Rs 10 each. Please guide me to validate the stamp paper and the agreement.