Gaya APA
Costinett, S., Byrd, D, R, H. (1994).
Spectrum 6 : A Communicative Course In English .
Englewood Cliffs:
Prentice Hall Regents.
Gaya MLA
Costinett, Sandra., Byrd, Donald, R, H.
"Spectrum 6 : A Communicative Course In English".
Englewood Cliffs:
Prentice Hall Regents,
1994.
Text.