Walter, James E.
Wadsworth, 1967
Buku Teks
Ray, George E.
Prentice-Hall, 1972
Buku Teks
Maurer, Herrymon, author
Macmillan, 1956
Buku Teks
Hoagland, Henry E.
McGraw-Hill Book Company, Inc., 1947
Buku Teks
Dewing, Arthur Stone
Ronald Press Co, 1953
Buku Teks