Mathiot, Madeleine
Indiana University Press, 1968
Buku Teks SO
University of Bath, 1985
Buku Referensi
Terry, Patrick D.
Addison-Wesley, 1986
Buku Teks SO
Alfonso, Anthony
Sophia University LL Center of Applied Linguistics, 1980
Buku Teks SO
Fishman, Joshua A.
Newbury House Publishers, 1972
Buku Teks SO