Update index.md

Author: dsyme

docs/index.md

@@ -24,6 +24,8 @@ Learning
 
 [Terminology](terminology.html) a reference for some of the terminology around F# async.
 
+[Comparison with IObservable](ComparisonWithIObservable.html) contains discussion about the difference between async sequences and IObservables.
+
 [API Reference](reference/index.html) contains automatically generated documentation for all types, modules and functions in the library. 
 This includes additional brief samples on using most of the functions.
 
@@ -43,4 +45,4 @@ redistribution for both commercial and non-commercial purposes. For more informa
   [gh]: https://github.com/fsprojects/FSharp.Control.AsyncSeq
   [issues]: https://github.com/fsprojects/FSharp.Control.AsyncSeq/issues
   [readme]: https://github.com/fsprojects/FSharp.Control.AsyncSeq/blob/master/README.md
-  [license]: https://github.com/fsprojects/FSharp.Control.AsyncSeq/blob/master/LICENSE.txt
+  [license]: https://github.com/fsprojects/FSharp.Control.AsyncSeq/blob/master/LICENSE.txt