Ogden, C. K. (Charles Kay), 1889-1957, author
Evans Brothers, [1940]
Buku Referensi
Walters, Morgan L
N.Y.Holt Rinehart and Winston,inc, 1966
Buku Teks
Agency for Cultural Affairs, [date of publication not identified]
Buku Referensi
Pollmann, Friedrich, author
Macmillan, 1976
Buku Referensi
consultant, Elaine Biech; editors, Jennifer Mitchell, Cat Russo
American Society for Training & Development, 2005
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