Sayre, Wallace S.
Brookings Institution, 1970
Buku Teks
Riesman, David, author
McGraw-Hill, 1975
Buku Teks
Committee on the Student in Higher Education
Hazen Foundation, 1968
Buku Teks
Van den Berghe, Pierre
Abelard-Schuman , 1970
Buku Teks
United Nations
United Nations, 1993
Buku Teks