Παραπομπή APA

Preston, R. J. (1961). North American trees (2nd ed.). Iowa State University press.

Παραπομπή Chicago Style

Preston, Richard J. North American Trees. 2nd ed. Iowa: Iowa State University press, 1961.

Παραπομπή MLA

Preston, Richard J. North American Trees. 2nd ed. Iowa State University press, 1961.