Lowndes, Douglas
Pergamon Press , 1969
Buku Teks
Aaker, David A., author
Prentice-Hall, 1987
Buku Teks
Marinaccio, Dave, author
Arcade Publishing, 2015
Buku Teks
Ahuja, B. N., author
Surjeet Publications, 1990
Buku Teks
Kirkpatrick, C.A., author
Houghton Miffiln, 1959
Buku Teks