North, Douglass C.
Harper & Row, 1971
Buku Teks SO
Tremblay, Victor J.
Springer, 2012
eBooks
Martin, Stephen, 1961-
Maxwell Macmillan International, 1994
Buku Teks
Burgess, Giles H.
Prentice-Hall, 1989
Buku Teks
Burgess, Giles H.
Prentice-Hall, 1989
Buku Teks