Busey, James L.
Random House, 1968
Buku Teks
Schmidt, Benno
GRIN Verlag GmbH, 2012
Buku Teks SO
edited by Fabio De Castro, Barbara Hogenboom, Michiel Baud
Palgrave Macmillan, 2016
Buku Teks
Colorado Westview Press. , 1989
Buku Teks
by James E. Anderson; David Brady; Charles Bullock III; Joseph stewart, JR
Brooks/Cole; cengage learning, 1984
Buku Teks