- "abacus," in A Dictionary of the English Language, by Samuel Johnson (1755)
- "Abacus," in The New Student's Reference Work, Chicago: F.E. Compton and Co. (1914)
- "Abacus," in A Dictionary of Greek and Roman Antiquities (v. 3rd), (ed.) by William Smith (1890)
- "Abacus," in Collier's New Encyclopedia, New York: P. F. Collier & Son Co. (1921)
- "Abacus," in Encyclopædia Britannica (11th ed., 1911)
- "Abacus," by John Weeks Moore in Complete Encyclopaedia of Music, Boston: Oliver Ditson Company (1880)
- "Abacus" in Dictionary of French Architecture from the 11th to 16th Century 1