(3)The approval of the Central Board of Direct Taxes or Chief Commissioner or Director General, as the case may be, granted before the 1st day of December, 2006 shall at any one time have effect for a period not exceeding three assessment years.Explanation. - For the purposes of this rule,-(i)"Chief Commissioner or Director General" means the Chief Commissioner or Director General whom the Central Board of Direct Taxes may, authorize to act as prescribed authority for the purposes of sub-clause (vi) or sub-clause (via) of clause (23C) of section 10 in relation to any fund or trust or institution;(ii)"Principal Commissioner or Commissioner" means the Principal Commissioner or Commissioner whom the Central Board of Direct Taxes may, authorize to act as prescribed authority for the purposes of sub-clause (vi) or sub-clause (via) of clause (23C) of section 10 in relation to any fund or trust or institution;(iii)"specified date" means the date which the Central Board of Direct Taxes may, by notification in the Official Gazette, specify in this behalf.