Walker, E. Ronald
University of Chicago Press, 1947
Buku Teks
Seth, M.L.
S. Chand, 1969
Buku Teks
edited by J.P. Nieuwenhuysen and P.J. Drake
Melbourne Unversity Press, 1977
Buku Teks
Hansen, Alvin Harvey, 1887-1975
McGraw-Hill, 1947
Buku Teks
Myrdal, Gunnar, 1898-
Routledge & Kegan Paul, 1955
Buku Teks