Grolier, Eric de, author
Unesco, 1979
Buku Teks
McFarlan, F. Warren (Franklin Warren), author
Rinehart and Winston, 1973
Buku Teks
Albrecht, Leon K., author
Macmillan, 1973
Buku Teks
Millett, John D., author
McGraw-Hill, 1959
Buku Teks
edited by David Eade; John Hodgson
North Holland Publishing Company, 1981
Buku Teks