Ok, Han-sok
Hanul books, 2009
Buku Referensi
Minshull, Roger
Hutchinson University Library, 1971
Buku Teks
Stamp, Laurence Dudley, 1898-1966
Methuen, 1950, 1952, 1967
Buku Teks
Heintzelman, Oliver H.
Prentice-Hall, 1960
Buku Teks
Heintzelman, Oliver H.
Prentice-Hall, 1965
Buku Teks