Stake, Robert E.
Sage Publications, 1995
Buku Teks
Lienhard, John H.,
Prentice Hall Englewood Cliffs, 1981
Buku Teks
Heimler, Charles H.
Charles E Merrill, 1977
Buku Teks
DePuy, Charles H.
John Wiley & Sons, 1975
Buku Teks
Sage Publications, 1980
Buku Teks