Raykov, Tenko
Routledge, Taylor & Francis Group, 2008
Buku Teks
Feinstein, Alvan R.
Yale University Press, 1996
Buku Teks
Kachigan, Sam Kash
Radius Press, 1991
Buku Teks
Dunteman, George Henry
Sage Publications, 1984
Buku Teks
Karson, Marvin J.
Iowa State University Press, 1982
Buku Teks