Volume for 1916 issued as House document 1169, 65th Cong., 2d sess.: 1951, pt. 1, 1952-53 issued as the Service's IRS publication (varies slightly).
Later information in the Service's publications on specific types of returns.
Issues for 1919-1923 available online at the FRASER web site. Address as of 2/26/06: http://fraser.stlouisfed.org/publications/income.
Also available online.
In 1954, split into: Statistics of income. Individual income tax returns; Statistics of income. Estate tax returns; Statistics of income. Corporation income tax returns; and Statistics of income. Fiduciary income tax returns.