Blalock, H. M. (1972). Casual inferences in nonexperimental research. Norton.
Lua i Stíl Chicago (17ú heag.)Blalock, Hubert M. Casual Inferences in Nonexperimental Research. New York: Norton, 1972.
Lua MLA (9ú heag.)Blalock, Hubert M. Casual Inferences in Nonexperimental Research. Norton, 1972.
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