Epstein, E.L.
Methuen, 1978
Buku Teks SO
Fromkin, Victoria A.
Holt, Rinehart and Winston, 1981
Buku Teks SO
Hazen, Kirk
Massachusetts : Wiley Blackwell, 2015
Buku Teks SO
Alfonso, Anthony
Sophia University LL Center of Applied Linguistics, 1980
Buku Teks SO
Argiielles, Alexander
Hollym International Corp, 2000
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