World Publishing Co, 1956
Buku Referensi
Scott-Kilvert, Ian, author
Longmans, Green, 1970
Buku Teks
Harrower, Elizabeth, 1928-, author
Angus & Robertson, 1966
Buku Teks
Merriam-Webster's, Incorporated, 1993
Buku Referensi
Merriam-Webster, 2000
Buku Referensi