Ploeg, Anton.,
Martinus Nijhoff, 1969
Buku Teks
Ploeg, A., author
Martinus Nijhoff, 1969
Buku Teks
Donnelly, Thomas C.
The University of New mexico Press, 1953
Buku Teks
Burns, James McGregor, author
Prentice-Hall, 1972
Buku Teks
Gujarati, Damodar N., author
McGraw-Hill, 1984
Buku Teks