Feather, Leonard, author
Horizon Press, 1960
Buku Referensi
edited by Kirsten Malmkjær, James M. Anderson
Routledge, 1991
Buku Referensi
Columbia University Press, 1950
Buku Referensi
edited by Vergilius Ferm
Littlefield, Adam and Co., 1959
Buku Referensi
Buku Teks