Peter Hui Marcus Schaefer Daniel Stefankovic Train Tracks and Confluent Drawings. 318-328 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3383&spage=318 2004 conf/gd/2004 Graph Drawing db/conf/gd/gd2004.html#HuiSS04