S. 139 : Return of income-Revised return-Once revised return is filed, Assessing Officer is not entitled to advert to original return of income-Loss-Loss to be allowed-Assessing Officer could not disturb apparent consideration by substituting agreed consideration by fair market value. [S. 2(11)32(i)(ii),43(6), 50, 72(1) 71(2), 74(1) 80, 139(3), 139(5), 143(3)]