UML Package Diagrams

[1] Package diagrams for "Classes, Data Entities and Use Cases" are emphasized
http://www.agilemodeling.com/artifacts/packageDiagram.htm

[2] Style Guidelines for drawing "Package Diagrams"
http://www.agilemodeling.com/style/packageDiagram.htm

[3] Introduction to "Package Diagrams"
http://www.sparxsystems.com.au/resources/uml2_tutorial/uml2_packagediagram.html