00291nam a2200121 a 450000500170000008200150001710000190003224500260005126000330007730000260011063000160013663000170015220251203091154.0  a511.5bBOL  aBollobas, Bela  aExternal graph theory  aLondonbAcademic pressc1978  axx,488 p.b22 cm.cHB  aMathematics  aGraph theory