1969—Pub. L. 91–172 redesignated first sentence of existing provisions as subsec. (a), and substantial portion of second sentence as subsec. (b)(1), and, in subsec. (b)(1) as so redesignated, inserted reference to section 512 of this title, and added pars. (2) and (3).

Amendment by Pub. L. 91–172 applicable to taxable years beginning after Dec. 31, 1969, see section 121(g) of Pub. L. 91–172, set out as a note under section 511 of this title.