Section, added Pub. L. 91–172, title VII, § 707(a), Dec. 30, 1969, 83 Stat. 674; amended Pub. L. 93–625, § 3(d), Jan. 3, 1975, 88 Stat. 2109, provided for an allowance of an amortization deduction for certain coal mine safety equipment, the method of election and termination of such deduction, the definition of term “certified coal mine safety equipment”, and special rules applicable to the amortization deduction.