Ghani, Noordin, author
Research Study Press, 1980
Buku Teks
Dollhoff, Terry, author
Reston Pub., 1979
Buku Teks
Clements, Alan, author
McGraw-Hill, 1991
Buku Referensi
Coffron, James W., author
Printice-Hall, 1981
Buku Teks
Halsall, Fred, author
Pitman, 1982
Buku Teks