Wortman, Sterling
To feed this world : the challenge and the strategy / Sterling Wortman, Ralph W. Cummings, Jr.
Johns Hopkins University Press, 1979
 Buku Teks
Phillips, Ralph W.
Livestock of china / Ralph W. Phillips
United states Government Printing Office, 1945
 Buku Teks
Tyler, Ralph W.
Basic principles of curriculum and instruction / Ralph W. Tyler
University of Chicago, 1949
 Buku Teks
Byrns, Ralph T
Exploring economics/ Ralph T. Byrns, Gerald W. Stone
Scott Foresman, 1984
 Buku Teks
Byrns, Ralph T.
Economics/ Ralph T. Byrns, Gerald W. Stone
Illinois, 1984
 Buku Teks
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