APA Style

MP., D, N, P., Ed.PhD, P, S, S. (1979). English Business Letters . : Longman.

MLA Style

MP., Drs., Ngalim, Purwanto,., Ed.PhD, Prof,H.D., Sudjana, S.,S,Pd.,M.. "English Business Letters". : Longman, 1979. Buku PGSD.