Wesley-Smith, Peter
Oxford University Press, 1987
Buku Teks
Artikel Jurnal
Hicks, George L.
Ubiters' & Publishers, 1989
Buku Teks SO
Osgood, Cornelius
The University of Arizona Press, 1975
Buku Teks SO
Cottrell, Robert
John Murray , 1993
Buku Teks SO