Yoakam, G. A., & Simpson, R. G. (1949). Directed study and observation of teaching (rev. ed.). Macmillan.
Chicago-viite (17. p.)Yoakam, Gerald Alan, ja Robert G. Simpson. Directed Study and Observation of Teaching. rev. ed. New York: Macmillan, 1949.
MLA-viite (9. p.)Yoakam, Gerald Alan, ja Robert G. Simpson. Directed Study and Observation of Teaching. rev. ed. Macmillan, 1949.
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