Chicago : The University of Chicago Press
Majalah, Jurnal, Buletin
Cambriage : The Massachussets Institute of Technologi (MIT) Press
Majalah, Jurnal, Buletin
Mader, Sylvia S., author
W.C. Brown , 1988
Buku Teks
Ostdiek, Vern J., author
Thomson Brooks/Cole, 2008
Buku Teks
Guba, Egon G., author
Jossey-Bass , 1981
Buku Teks