Adams, Walter, 1922-1998
Macmillan, 1957
Buku Teks
Gunton, George
Appelton and Company , 1899
Buku Teks
Stocking, George W.
The Twentieth Century Fund, 1948
Buku Teks
edited by Edwin Mansfield
W.W. Norton, 1964
Buku Teks
Machlup, Fritz
The Johns Hopkins Press, 1952
Buku Teks