Lewis, William Draper, author
Michie, 1937
Buku Teks
edited by Hasting Donnan
SAGE Publication, 2002
Buku Teks
Hartshorn, Truman Asa, author
John Wiley & Sons, 1980
Buku Teks
edited by Vic Barnett
John Wiley & Sons, 1981
Buku Teks
edited by Norman K. Denzin, Yvonna S. Lincoln
Sage, 1998
Buku Teks