21
by Heathcock, Claude L.
Published 1963
22
by Sawer, Geoffrey
Published 1975
23
by Pritchett, C. Herman, 1907-
Published 1959
24
by Abdul Aziz Bari
Published 2001
25
Published 1948
26
27
28
Published 2007
29
by Kommers, Donald P.
Published 1989
30
Published 1991
31
Published 1992
32
33
by Abdul Aziz Bari
Published 2002
34
by Stephens, Otis H., Jr.
Published 2003
35
Published 1988
36
Published 1990
37
Published 2001
38
by Boyd J. Patrick
Published 2005
39
by Mason, Alpheus Thomas, 1899-
Published 1990
40
Published 2012