AbstractClasses illustrated
* http://www.gnacademy.org/twiki/bin/view/CPP/AbstractClasses ''[BrokenLink 9-17-2009]''
* http://www.gnacademy.org/twiki/bin/view/CPP/AbstractClassesAgain ''[BrokenLink 9-17-2009]''
* http://msdn.microsoft.com/en-us/library/k535acbf.aspx
* http://www.javaworld.com/javaworld/javaqa/2001-04/03-qa-0420-abstract.html
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CategoryAbstraction