Helmut Kofler Ernst J. Haunschmid Wilfried N. Gansterer Christoph W. Ueberhuber The Locality Property in Topological Irregular Graph Hierarchies. 437-449 1999 conf/acpc/1999 ACPC http://link.springer.de/link/service/series/0558/bibs/1557/15570437.htm db/conf/acpc/acpc1999.html#KoflerHGU99