Allen, Edward David, 1923-
Harcourt Brace Jovanovich, c1977
Buku Teks SO
editedby Barbara Kroll
Cambridge University Press, 1990
Buku Teks SO
edited by Barbara Kroll
Cambridge University Press, 1990
Buku Teks
Artikel Jurnal
Ohta, Amy Snyder
Lawrence Erlbaum Associates, 2001
Buku Teks SO