Fix a very minor (but annoying when looking for things!) markup nit.
diff --git a/Doc/ref/ref1.tex b/Doc/ref/ref1.tex
index 37fbad7..d6bb8b2 100644
--- a/Doc/ref/ref1.tex
+++ b/Doc/ref/ref1.tex
@@ -33,6 +33,7 @@
 built-in modules are mentioned when they interact in a significant way
 with the language definition.
 
+
 \section{Notation\label{notation}}
 
 The descriptions of lexical analysis and syntax use a modified BNF