TY  - BOOK
AU  - Helmers,Scott A.
TI  - Data communications: a beginner's guide to concepts and technology 
SN  - 0131988700
PY  - 1989///
CY  - Englewood Cliffs, N.J. : 
PB  - Prentice Hall, 
KW  - Computer networks
KW  - Data transmission systems
N1  - Includes index; Bibliography: p. 277-282
ER  -