Andrew, Nancy Learmonth, compiled
Frederick Warne & Co , 1973
Buku Referensi
edited by Susan Bambrick
Cambridge University Press, 1994
Buku Referensi
Crawford, R. M.
Hutchinson's University Library, 1955
Buku Teks
Crawford, R.M., author
Hutchinson University Library, 1952.
Buku Teks
Princeton University Press, 1944
Buku Teks