Robertson, Ross M.
Harcourt, Brace & World, 1964
Buku Teks
Davis, Lance E.
Richard D. Irwin, 1965
Buku Teks
Colm, Gerhard
National Planning Association , 1961
Buku Teks
Reynold, Lloyd George
McGraw-Hill, 1981
Buku Teks
Salvadori, Massimo
Bobbs-Merrill, 1963
Buku Teks