Burns, James McGregor, author
Prentice-Hall, 1972
Buku Teks
Ploeg, Anton.,
Martinus Nijhoff, 1969
Buku Teks
Gujarati, Damodar N., author
McGraw-Hill, 1984
Buku Teks
Hall, Ford P.
McGraw-Hill Book Company,Inc., 1949
Buku Teks
Burns, James McGregor, author
Prentice-Hall, 1989
Buku Teks