CRC-Cards and Roleplay Diagramms---Informal Tools to
Teach OO Thinking
J. Börstler. Proceedings $2^nd$ CeTUSS Workshop on Computer Science
Education, Linköping, Sweden, (April 2007)http://www.cs.umu.se/~jubo/Papers/CRC_CeTUSS07.pdf
-- last visited $11^th$ January 2008.