Walker, A. L., Roach, J. K., & Hanna, J. M. (1979). How to use adding and calculating machines (4th ed.). Gregg Division, McGraw-Hill.
Lua i Stíl Chicago (17ú heag.)Walker, Arthur L., J. Kenneth Roach, agus J. Marshall Hanna. How to Use Adding and Calculating Machines. 4th ed. New York: Gregg Division, McGraw-Hill, 1979.
Lua MLA (9ú heag.)Walker, Arthur L., et al. How to Use Adding and Calculating Machines. 4th ed. Gregg Division, McGraw-Hill, 1979.
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