Gaya APA
Helmers, S, , A. (1989).
Data cummunications, a begineers guide to concepts and technology .
New Jersey:
Prentice Hall.
Gaya MLA
Helmers, Scott, , A..
"Data cummunications, a begineers guide to concepts and technology".
New Jersey:
Prentice Hall,
1989.
Printed Book.