editors, John M. Last, Robert B. Wallace ; associate editors, Elizabeth Barrett-Connor [and others]
Appleton & Lange, 1992
Buku Referensi
Penalver, Rafael A., author
Arco Publishing, 1984
Buku Teks SO
Penalver, Rafael A., author
Arco Publishing, Inc., 1981
Buku Teks SO
edited by Philip E. Sartwell
Meredith Publ., 1965
Buku Teks SO
Smillie, Wilson G.
Macmillan, 1963
Buku Teks SO