Halpern, Manfred
Princeton University Press, 1963
Buku Teks
edited by David E. Long and Bernard Reich
Westview Press, 1986
Buku Teks
edited by David E. Long and Bernard Reich
Westview Press, 2002
Buku Teks
Artikel Jurnal
Palmer, Monte
Thomson Wadsworth, 2007
Buku Teks