Funk & Wagnalls Company, 1949
Buku Teks
Le Brefon, Preston P.
Holt, Rinehart and Winston, 1965
Buku Teks
Walters, Jack Edward
Littlefield, Adams, 1959
Buku Teks
Schonberger, Richard John, author
The Free Press , 1982
Buku Teks
Pergamon Press, 1960
Buku Teks