Reactivating graphical subjectsMägi, ReinProceedings of the 19th Conference Geometry Graphics Computer : Silesian University of Technology in Gliwice, Ustron, 25th-27th June 20122012 / p. 43 http://ogigi.polsl.pl/zeszyt_Ustron_12/REFERATY%20USTROŃ%202012%20PDF/Magi.pdf