@ -37,6 +37,7 @@ Original Source: [Free Programming books](http://stackoverflow.com/revisions/392
* [Delphi / Pascal](#delphi--pascal)
* [DTrace](#dtrace)
* [Elasticsearch](#elasticsearch)
* [Elixir](#elixir)
* [Emacs](#emacs)
* [Erlang](#erlang)
* [F#](#f-sharp)
@ -888,6 +889,12 @@ Original Source: [Free Programming books](http://stackoverflow.com/revisions/392
* [Elasticsearch: The Definitive Guide](http://www.elasticsearch.org/guide/en/elasticsearch/guide/current/index.html) ([fork it on GH](https://github.com/elasticsearch/elasticsearch-definitive-guide))