Index: doc/aaron_comp_II/comp_II.tex
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 Ganzinger and Ripken~\cite{Ganzinger80} propose an approach (later refined by Pennello \etal~\cite{Pennello80}) that uses a top-down filtering pass followed by a bottom-up filtering pass to reduce the number of candidate interpretations; they prove that for the Ada programming language a small number of such iterations is sufficient to converge to a solution for the expression resolution problem. 
-Their algorithm differs from the hybrid approach under investigation in that it takes multiple passes over the expression tree to yield a solution, but is otherwise similar.
+Persch \etal~\cite{PW:overload} developed a similar two-pass approach where the bottom-up pass is followed by the top-down pass. 
+These algorithms differ from the hybrid approach under investigation in that they take multiple passes over the expression tree to yield a solution, and also in that they apply both filtering heuristics to all expression nodes, an optimization defeated by \CFA's polymorphic functions and implicit conversions.
 
 \subsubsection{Common Subexpression Caching}