Truesdell, L. E. (1965). The development of punch card tabulation in the Bureau of the Census, 1890-1940, with outlines of actual tabulation programs/ Leon Edgar Truesdell. U.S. Dept. of Commerce.
Lua i Stíl Chicago (17ú heag.)Truesdell, Leon Edgar. The Development of Punch Card Tabulation in the Bureau of the Census, 1890-1940, with Outlines of Actual Tabulation Programs/ Leon Edgar Truesdell. Washington: U.S. Dept. of Commerce, 1965.
Lua MLA (9ú heag.)Truesdell, Leon Edgar. The Development of Punch Card Tabulation in the Bureau of the Census, 1890-1940, with Outlines of Actual Tabulation Programs/ Leon Edgar Truesdell. U.S. Dept. of Commerce, 1965.
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