update doc

doc/user_manual/PostProcessors/HS2PS.tex

@@ -3,8 +3,9 @@ \subsubsection{HS2PS}
 
 This Post-Processor performs a conversion from HistorySet to PointSet.
 The conversion is made so that each history $H$ is converted to a single point $P$.
-Assume that each history $H$ is a dict of $n$ output variables $x_1=[...],x_n=[...]$, then the resulting point $P$ is $P=concat(x_1,...,x_n)$.
-Note: it is here assumed that all histories have been sync so that they have the same length, start point and end point. If you are not sure, do a pre-processing the the original history set.
+Assume that each history $H$ is a dictionary (mapping) of $n$ output variables $x_1=[...],x_n=[...]$, then the resulting point $P$ is $P=concat(x_1,...,x_n)$.
+Note: it is here assumed that all histories have been synced so that they have the same length, start point and end point. 
+If you are not sure, do a pre-processing the the original history set.
 
 \ppType{HS2PS}{HS2PS}