-. (1989). Nature's wonderlands: National park of the world. National geography society.
Chicago Style aipamena-. Nature's Wonderlands: National Park of the World. Washington: National geography society, 1989.
MLA aipamena-. Nature's Wonderlands: National Park of the World. National geography society, 1989.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.