Dickinson, Robert E.
Routledge & Kegan Paul Limited, 1951
Buku Teks
Meller, Helen
John Wiley & Sons, 2001
Buku Teks
Ennen, Edith
North-Holland Publishing, 1979
Buku Teks
Tanghe, Jan
Pegamon Press, 1984
Buku Referensi
Oxford University Press, 2002
Buku Teks