Obourn, E. S. (1963). Discovering the world of science. D. Van Nostrand.
Lua i Stíl Chicago (17ú heag.)Obourn, Ellsworth S. Discovering the World of Science. Princeton, NJ: D. Van Nostrand, 1963.
Lua MLA (9ú heag.)Obourn, Ellsworth S. Discovering the World of Science. D. Van Nostrand, 1963.
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