Heck, Ronal H., author
Routledge, 2014
Buku Teks
editor, Garrett Fitzmaurice, Marie Davidian, Geert Verbeke, Geert Molenberghs
CRC Press , 2009
Buku Referensi
Little, Todd D, author
The Guilford Press, 2013
Buku Teks
Singer, Judith A., author
Oxford University Press, 2003
Buku Teks
edited by Roger Penn, Damon Berridge
Sage, 2013
Buku Teks SO