Update Additional-Reading.md

fix dead link

Author: akarnokd

docs/Additional-Reading.md

@@ -3,7 +3,7 @@ A more complete and up-to-date list of resources can be found at the [reactivex.
 # Introducing Reactive Programming
 * [Introduction to Rx](http://www.introtorx.com/): a free, on-line book by Lee Campbell **(1.x)**
 * [The introduction to Reactive Programming you've been missing](https://gist.github.com/staltz/868e7e9bc2a7b8c1f754) by Andre Staltz
-* [Mastering Observables](http://docs.couchbase.com/developer/java-2.0/observables.html) from the Couchbase documentation **(1.x)**
+* [Mastering Observables](https://docs.huihoo.com/couchbase/developer-guide/java-2.0/observables.html) from the Couchbase documentation **(1.x)**
 * [Reactive Programming in Java 8 With RxJava](http://pluralsight.com/training/Courses/TableOfContents/reactive-programming-java-8-rxjava), a course designed by Russell Elledge **(1.x)**
 * [33rd Degree Reactive Java](http://www.slideshare.net/tkowalcz/33rd-degree-reactive-java) by Tomasz Kowalczewski **(1.x)**
 * [What Every Hipster Should Know About Functional Reactive Programming](http://www.infoq.com/presentations/game-functional-reactive-programming) - Bodil Stokke demos the creation of interactive game mechanics in RxJS