APA

Colbert E. H., . (1958). Millions of years ago. New york: Crowell.

Chicago

Colbert Edwin Harris, . 1958. Millions of years ago. New york: Crowell.

Harvard

Colbert E. H., . (1958). Millions of years ago. New york: Crowell.

MLA

Colbert Edwin Harris, . Millions of years ago. New york: Crowell. 1958.