Effective Date of 1964 Amendment
[Pub. L. 88–272, title II, § 227(c)], Feb. 26, 1964, [78 Stat. 98], provided that: “The amendments made by this section [amending this section and sections 631, 1016, 1231, and 1402 and section 411 of Title 42, The Public Health and Welfare] shall apply with respect to amounts received or accrued in taxable years beginning after December 31, 1963, attributable to iron ore mined in such taxable years.”