Hempel, C. G. (1966). Philosophy of natural science. Prentice-Hall.
Lua i Stíl Chicago (17ú heag.)Hempel, Carl Gustav. Philosophy of Natural Science. Englewood Cliffs, N.J: Prentice-Hall, 1966.
Lua MLA (9ú heag.)Hempel, Carl Gustav. Philosophy of Natural Science. Prentice-Hall, 1966.
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