Kephart, Newell C.
McGraw-Hill Book Company,INC, 1952
Buku Teks
Kador, John, author
McGraw-Hill, 2002
Buku Teks
Domi C. Matutina
Rineka Cipta, 1993
Buku Teks
Davis, Norah M.
Nicholson & Watson, 1946
Buku Teks
Gillham, Bill, author
Continuum, 2000
Buku Teks