Laski, Harold J., author
George Allen and Unwin, 1957
Buku Teks
Lee, Hansol H.B.
Oxford University Pres, 1989
Buku Referensi
Crocker, Mary E. Coffman, author
McGraw-Hill, 1990
Buku Teks
Jespersen, Otto, author
George Allen and Unwin, 1933
Buku Teks
Jesperson, Otto
George Allen and Unwin, 1951
Buku Teks