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README.md

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 # Student, Instructor, Classroom
-* **Purpose** - to demonstrate the use of [Java interfaces](http://tutorials.jenkov.com/java/interfaces.html)
+* **Purpose** - to demonstrate the use of [Java interfaces](http://tutorials.jenkov.com/java/interfaces.html#java-interface-example)
 * **Objective** - to implement a `ZipCodeWilmington` _singleton_ which _mediates_ a _composite_ `Students` and `Instructors` reference.