...section 251 is taxable only on its gross income from sources within the United States by reason of its receiving a large percentage of its gross income from sources within a possession of the United States. The credit under section 26 (b) (that Is, the sum of the credits determined under paragraphs...

...Foreign corporations. (3) Corporations organized under the China Trade Act, 1922. (4) Corporations entitled to the benefits of section 251, by reason of receiving a large percentage of their income from possessions of the United States. (5) Personal service corporations. (6) Insurance...