Cita APA (7th ed.)

Callahan, D., & Engelhardt, H. T. (1981). The Roots of ethics: Science, religion, and values. Plenum Press.

Cita Chicago (17th ed.)

Callahan, Daniel, i Hugo Tristram Engelhardt. The Roots of Ethics: Science, Religion, and Values. New York: Plenum Press, 1981.

Cita MLA (9th ed.)

Callahan, Daniel, i Hugo Tristram Engelhardt. The Roots of Ethics: Science, Religion, and Values. Plenum Press, 1981.