APA
William L. Allen E. R. M. P. E. E. &. R. L. B. M. E., . (2001). National Geographic. Holland: Joseph M. Anderson.
Chicago
William L. Allen Ed Robert M Poole Executive Editor & Robert L Booth Managing Editor, . 2001. National Geographic. Holland: Joseph M. Anderson.
Harvard
William L. Allen E. R. M. P. E. E. &. R. L. B. M. E., . (2001). National Geographic. Holland: Joseph M. Anderson.
MLA
William L. Allen Ed Robert M Poole Executive Editor & Robert L Booth Managing Editor, . National Geographic. Holland: Joseph M. Anderson. 2001.
