Calder, N. (1973). Nature in the round: A guide to environmental science. Viking Press.
Lua i Stíl Chicago (17ú heag.)Calder, Nigel. Nature in the Round: A Guide to Environmental Science. New York: Viking Press, 1973.
Lua MLA (9ú heag.)Calder, Nigel. Nature in the Round: A Guide to Environmental Science. Viking Press, 1973.
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