Added link to Controlling Relevance to relevance intro

Author: clintongormley

056_Sorting/90_What_is_relevance.asciidoc

@@ -17,8 +17,8 @@ were found, but what we usually mean by _relevance_ is the algorithm that we
 use to calculate how similar the contents of a full text field are to a full
 text query string.
 
-The standard _similarity algorithm_ used in Elasticsearch is known as TF/IDF,
-or Term Frequency/Inverse Document Frequency, which takes the following
+The standard _similarity algorithm_ used in Elasticsearch is known as  _Term
+Frequency/Inverse Document Frequency_, or _TF/IDF_, which takes the following
 factors into account:
 
 Term frequency::
@@ -51,6 +51,9 @@ When multiple query clauses are combined using a compound query like the
 `bool` query, the `_score` from each of these query clauses is combined to
 calculate the overall `_score` for the document.
 
+TIP: We have a whole chapter dedicated to relevance calculations and how to
+bend them to your will in <<controlling-relevance>>.
+
 [[explain]]
 ==== Understanding the score