Stanford University Press, 1969
Buku Teks
Klaus, Marshall H.
Mosby Comp., 1982
Buku Teks SO
Klaus, Marshall H.
Mosby Comp., 1982
Buku Teks SO
Robert Maynard Hutchins, editor in chief
Encyclopaedia Britannica, Inc., 1952
Buku Referensi
Encyclopaedia Britannica, Inc., 1952
Buku Referensi