Shell, Marc, author
The Johns Hopkins University Press, 1978
Buku Teks
Wicksell, Knut
George Routledge and Sons , 1946
Buku Teks
Paolo Janni
The council for research in values and philoaophy, 2001
Buku Teks
Schiller, Bradley R., author
Prentice-Hall, 1975
Buku Teks
Robinson, Marshall A., author
Brookings Institution, 1955
Buku Teks