S. 55A : Capital gains-Reference to valuation officer-Long term capital gains-Valuation as on 1-4-1981-Amendment to section 55A(a) inserted with effect from 1-7-2012 by Finance Act, 2012 providing for making reference by AO to DVO for determination of value of property sold by assessee was not applicable retrospectively. [S. 45, 50C, 55A(a)]