edited by Robert M. Hashway
Praeger, 1990
Buku Referensi
Stoff, Sheldon Ptaschevitch
Harper & Row , 1969
Buku Teks
Marland, Sidney P.
McGraw-Hill, 1974
Buku Teks
Department of Health, education and welfare, 1964
Buku Teks
Hallahan, Daniel P.
Prentice-Hall, 1988
Buku Teks