21
Published 1999
22
Published 2008
23
Published 2014
24
25
26
Published 2008
27
by Copestake, Stephen
Published 2002
28
29
by Wang, Xin
Published 2005
30
Published 2004
31
by Zhao, Shi Long
Published 2004
32
by Carver, D.K.
Published 1979
33
Published 1992
34
by Cohen, Akiba A.
Published 1987
35
36
Published 2006
37
by Sabariah Abdullah
Published 2006
38
Published 1994
39
Published 2002
40