Gummesson, Evert
Sage Publications, Inc., 2000
Buku Teks
edited by Peter Reason, Hilary Bradbury
Sage , 2013
Buku Referensi
Steven S. Coughlin, Selina A. Smith, and Maria E. Fernandez, editors
Oxford University Press, 2017
eBooks
Pertti J, Pelto
Cambridge University Press, 2012
eBooks
edited by George J. McCall, J.L. Simmons.
Random House, 1969
Buku Teks