1. A new shape factor;Danielsson;Computer Graphics Image Processing,1978
2. Merkmale fuer die Segmentation von Dokumenten zur automatischen Textverabeitung;Wahl,1981
3. Procedures for an Automatic Segmentation of Text, Graphic and Halftone Regions in Documents;Abele,1981
4. Distance functions on digital pictures;Rosenfeld;Pattern Recognition,1968
5. Digital Picture Processing;Rosenfeld,1976