Amendment to section 80HH narrows eligibility by adding a pre April 1, 1990 cut off to the earlier 1970 reference. Amendment imposes a temporal limitation on section 80HH by inserting the words 'but before the 1st day of April, 1990' after the reference to 'the 31st day of December, 1970' in sub section (2)(i) and sub section (3)(i), thereby restricting the period to which the relevant entitlement or condition applies.