APA
Udall S. L., . (1966). National parks of America. New York: G. P. Putnam's Sons.
Chicago
Udall Stewart L, . 1966. National parks of America. New York: G. P. Putnam's Sons.
Harvard
Udall S. L., . (1966). National parks of America. New York: G. P. Putnam's Sons.
MLA
Udall Stewart L, . National parks of America. New York: G. P. Putnam's Sons. 1966.