Pusat Kajian Ilmu Ekonomi (Puskanomi) Universitas Indraprasta PGRI, 2016
Majalah, Jurnal, Buletin
Arya, Jagdish C.
Prentice-Hall, 1981
Buku Teks SO
Brown, E.H. Phelps
Sir Isaac Pitman & Sons, 1953
Buku Teks SO
Wessel, Robert H.
Henry Holt, 1959
Buku Teks SO
Mills, Richard L.
McGraw-Hill Kogakusha, 1977
Buku Teks SO