Stoff, Sheldon Ptaschevitch, author
Harper & Row , 1969
Buku Teks
London : William Clowes and Sons Ltd
Majalah, Jurnal, Buletin
Smith, L. Glenn, author
Allyn and Bacon, 1973
Buku Teks
Dubin, Robert, author
Prentice-Hall, 1968
Buku Teks
Harper,
Buku Teks