Ok, Han-sok
Hanul books, 2009
Buku Referensi
by Christopher L. Salter ... [et al.]
Saunders College, 2000
Buku Teks SO
Minshull, Roger
Hutchinson University Library, 1971
Buku Teks SO
Harris, D.D.
Whitcombe Tombs, 1963
Buku Teks SO
White, C. Langdon
Prentice-Hall, 1943
Buku Teks SO