Section 80S amendment clarifies applicability to specified sub clauses of section 28, retrospective from 1 April 1972. The amendment substitutes the cross-reference in section 80S: replacing the words 'provisions of clause (ii) of section 28' with 'provisions of sub clause (a) or sub clause (b) or sub clause (c) of clause (ii) of section 28,' and declares that substitution to be effective from 1 April, 1972.