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
Zhao, Rukuo
Chau Ju-Kua: his work on the Chinese and Arab trade in the twelfth and thirteenth centuries, entitled Chu-fanchiÌ / Zhao Rukuo Translated from the Chinese and annotated by Friedrich Hirth and W. W. Rockhill.
Paragon Book Reprint Corp, 1966
 Buku Teks
Wortman, Sterling
To feed this world : the challenge and the strategy / Sterling Wortman, Ralph W. Cummings, Jr.
Johns Hopkins University Press, 1979
 Buku Teks