M. Carmen Hernando Michael E. Houle Ferran Hurtado On Local Transformation of Polygons with Visibility Properties. 54-63 2000 conf/cocoon/2000 COCOON http://link.springer.de/link/service/series/0558/bibs/1858/18580054.htm db/conf/cocoon/cocoon2000.html#HernandoHH00