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README.md

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 # Leon's Lengthy Learner Lab 
-* **Purpose** - to demonstrate the use of [Java interfaces](http://tutorials.jenkov.com/java/interfaces.html#java-interface-example)
+* **Purpose** - to demonstrate the use of
+	* [interfaces](https://stackoverflow.com/questions/1321122/what-is-an-interface-in-java)
+	* [abstract classes](https://stackoverflow.com/questions/1320745/abstract-class-in-java)
+	* [concrete classes](https://stackoverflow.com/questions/43224901/what-is-the-concrete-class-in-java)
+	* [enums](https://stackoverflow.com/questions/4709175/what-are-enums-and-why-are-they-useful)
+	* [generics](https://stackoverflow.com/questions/7815528/what-are-generics-in-java/7815579)
 * **Objective** - to implement a `ZipCodeWilmington` class which _mediates_ a _composite_ `Students` and `Instructors` _singleton_ reference.