Section 2(3)(a) in Central Excise Laws (Amendment and Validation) Act, 1982
(a)it shall be necessary for the purpose of granting, by any notification or order, any exemption from any duty of excise, or fixing, by any notification or order, any rate of duty, leviable under such Central law to expressly refer to the provisions of the said Central law in the preamble to such notification or order, or to state by express words in such notification or order that the exemption provided for, or the rate of duty fixed, by such notification or order is an exemption from, or the rate of duty under, such Central law;