DUPREE, H. D. E. (1966). MODERN COLLEGE TRIGONOMETRY. Dickenson Publishing Company.
Lua i Stíl Chicago (17ú heag.)DUPREE, HARMON DANIEL E. MODERN COLLEGE TRIGONOMETRY. Dickenson Publishing Company, 1966.
Lua MLA (8ú heag.)DUPREE, HARMON DANIEL E. MODERN COLLEGE TRIGONOMETRY. Dickenson Publishing Company, 1966.
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