Penalver, Rafael A.
Arco Publishing, 1984
Buku Teks SO
Penalver, Rafael A.
Arco Publishing, Inc., 1981
Buku Teks SO
edited by Philip E. Sartwell
Meredith Publ., 1965
Buku Teks
editors, John M. Last, Robert B. Wallace ; associate editors, Elizabeth Barrett-Connor [and others]
Appleton & Lange, 1992
Buku Referensi
edited by Edwin D. Kilbourne, Wilson G. Smillie
MacMillan company, 1969
Buku Teks SO