WIJEWICKREMA, Sudanthi N. R. a PAPLIŃSKI, Andrew P. Principal component analysis for the approximation of an image as an ellipse. Václav Skala - UNION Agency, 2005. Dostupné také z: http://wscg.zcu.cz/WSCG2005/Papers_2005/Poster/!WSCG2005_Poster_Proceedings_Final.pdf.