Cohen, D. (1994). Precalculus with unit-circle trigonometry (2nd ed.). West Publishing Company.
Lua i Stíl Chicago (17ú heag.)Cohen, David. Precalculus with Unit-circle Trigonometry. 2nd ed. Minneapolis, NY: West Publishing Company, 1994.
Lua MLA (9ú heag.)Cohen, David. Precalculus with Unit-circle Trigonometry. 2nd ed. West Publishing Company, 1994.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.