Harris, Norman C., author
McGraw-Hill, 1980
Buku Teks
Standing Conference of Principals
Standing Conference of Principals, 1987
Buku Referensi
Weinig, Arthur J., author
John Wiley & Sons, 1939
Buku Teks
Snedecor, George W., author
The Iowa State University Press, 1964
Buku Teks
Leach, John, 1953-
Philadelphia Open University Press 1991,
Buku Teks