21
22
by Lewis
Published 2008
23
by Weaver
Published 1948
24
by Spengler
Published 2002
25
by Schweitzer
Published 1987
26
by Boorstin
Published 1998
27
by Boorstin
Published 1993
28
29
by Gribbin
Published 2005
30
31
Published 1992
32
by Lipson
Published 1993
33
by Tainter
Published 1988
34
35
by Winks
Published 1992
36
by Adler
Published 2006
37
by Allchin, Bridget
Published 1982
38
by Mohd. Yusof Hasan
Published 1991
39
by Anuar Ibrahim
Published 1996
40
by Kraemer
Published 1992