000 00305nam a2200121Ia 4500
008 221221s9999 xx 000 0 und d
020 _a9788131708729
082 _a004
_bHEL/U
100 _aHeld, Gilbert
245 0 _aUnderstanding Data Communications
260 _aNew Delhi
_bPearson
_c2013
942 _cBK
999 _c33719
_d33719