APA

Callahan D., Engelhardt H. T., . (1981). The roots of ethics: science, religion, and values. New York: Plenum Press.

Chicago

Callahan Daniel, Engelhardt H Tristram, . 1981. The roots of ethics: science, religion, and values. New York: Plenum Press.

Harvard

Callahan D., Engelhardt H. T., . (1981). The roots of ethics: science, religion, and values. New York: Plenum Press.

MLA

Callahan Daniel, Engelhardt H Tristram, . The roots of ethics: science, religion, and values. New York: Plenum Press. 1981.