Sec. 521. Exemption of farmers' cooperatives from tax. [522. Repealed.] AMENDMENTS 1969 - Pub. L. 91-172, title I, Sec. 101(a), Dec. 30, 1969, 83 Stat. 492, substituted "PART IV" for "PART III" as part designation. 1962 - Pub. L. 87-834, Sec. 17(b)(5), Oct. 16, 1962, 76 Stat. 1051, struck out item 522 "Tax on farmers' cooperatives".