Penalver, Rafael A.
Arco Publishing, 1981
Buku Teks
editors, John M. Last, Robert B. Wallace ; associate editors, Elizabeth Barrett-Connor [and others]
Appleton & Lange, 1992
Buku Referensi
edited by Philip E. Sartwell
Meredith Publ., 1965
Buku Teks
Smillie, Wilson G.
Macmillan, 1963
Buku Teks
edited by John M. Last
D. Appleton-Century, 1980
Buku Teks