Extreme Programming EXPlained: Embrace Change,Kent Beck,1999 Agile Software Development, Principles, Patterns, and Practices,Robert C. Martin,2002 Test Driven Development: By Example ,Kent Beck, 2002 Refactoring: Improving the Design of Existing Code,Martin Fowler, Kent Beck,1999 Testing Things That Seem Hard to Test,Robert S. Koss ,2001