[Design Patterns] Erich Gamma . Richard Helm . Ralph Johnson . John Vlissides . 0201633612 . 1995 . Design Patterns: Elements of Reusable Object-Oriented Software .

[Strategy Design Pattern] Erich Gamma . Richard Helm . Ralph Johnson . John Vlissides . 0201633612 . 315-324 . 1995 . Design Patterns: Elements of Reusable Object-Oriented Software . Strategy .

[Visitor Design Pattern] Erich Gamma . Richard Helm . Ralph Johnson . John Vlissides . 0201633612 . 331-344 . 1995 . Design Patterns: Elements of Reusable Object-Oriented Software . Visitor .

[Refactoring] Martin Fowler . 0201485672 . 1999 . Refactoring: Improving the Design of Existing Code .

[Replace Parameter With Method] Martin Fowler . 0201485672 . 292-294 . 1999 . Refactoring: Improving the Design of Existing Code .

[Introduce Null Object] Martin Fowler . 0201485672 . 260-266 . 1999 . Refactoring: Improving the Design of Existing Code .