Index: doc/aaron_comp_II/comp_II.tex
===================================================================
--- doc/aaron_comp_II/comp_II.tex	(revision 7bb37fc39aa6b85202a689dec1bc67868466220f)
+++ doc/aaron_comp_II/comp_II.tex	(revision e3d1cc1cc41dfd30d0ace9e1dc26baf3cf303ced)
@@ -462,4 +462,7 @@
 
 Deciding when to switch between bottom-up and top-down resolution to minimize wasted work in a hybrid algorithm is a necessarily heuristic process, and though finding good heuristics for which subexpressions to swich matching strategies on is an open question, one reasonable approach might be to set a threshold $t$ for the number of candidate functions, and to use top-down resolution for any subexpression with fewer than $t$ candidate functions, to minimize the number of unmatchable argument interpretations computed, but to use bottom-up resolution for any subexpression with at least $t$ candidate functions, to reduce duplication in argument interpretation computation between the different candidate functions. 
+
+Ganzinger and Ripken~\cite{Ganzinger80} propose an approach 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.
 
 \subsubsection{Common Subexpression Caching}