APA

Ehrlich P. R., Ehrlich A. H., Holdren J. P. & Holdren J. P. (1973). Human ecology. San Francisco, Calif: Freeman.

Chicago

Ehrlich Paul R, Ehrlich Anne H, Holdren John Paul and Holdren John P. 1973. Human ecology. San Francisco, Calif: Freeman.

Harvard

Ehrlich P. R., Ehrlich A. H., Holdren J. P. and Holdren J. P. (1973). Human ecology. San Francisco, Calif: Freeman.

MLA

Ehrlich Paul R, Ehrlich Anne H, Holdren John Paul and Holdren John P. Human ecology. San Francisco, Calif: Freeman. 1973.