Lofland, John, author
Wadsworth, 1984
Buku Teks
Corinne Martin
VS Verlag, 2012
eBooks
edited by Rosa Lasaponara and Nicola Masini
Springer, 2012
eBooks
Stephenson, D. J. (Derek John), author
Newnes, 1994
Buku Referensi
Ludwig, Allan I.
Middletown Wesleyan University Press 1966
Buku Teks