1
by Sagoff
Published 2008
2
3
by Barbier
Published 2005
4
5
by Le More
Published 2008
6
by Caplan
Published 2007
7
by Howell
Published 1993
8
Published 2008
9
Published 2006
10
11
12
by al-Maliki
Published 2001
13
Published 1999
14
15
16
by Kotler
Published 2015
17
18
by Brux
Published 2016
19
by Sjoberg
Published 1991
20
Published 1993