TY  - GEN
AU  - Held,Gilbert
AU  - Friend,George E.
TI  - Understanding data communications
SN  - 0672300052
U1  - 004.6 
PY  - 1991///
CY  - Indianapolis, Ind.
PB  - Sams Pub.
KW  - Data transmission systems
KW  - Computer networks
ER  -