Lyudmil Aleksandrov Anil Maheshwari Jörg-Rüdiger Sack An Improved Approximation Algorithm for Computing Geometric Shortest Paths. 246-257 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2751&spage=246 2003 conf/fct/2003 FCT db/conf/fct/fct2003.html#AleksandrovMS03