Index: doc/aaron_comp_II/comp_II.tex
===================================================================
--- doc/aaron_comp_II/comp_II.tex	(revision ce2fed5c215f38532f3b35f6b5caff6e87457e91)
+++ 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}
Index: doc/bibliography/cfa.bib
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--- doc/bibliography/cfa.bib	(revision ce2fed5c215f38532f3b35f6b5caff6e87457e91)
+++ doc/bibliography/cfa.bib	(revision e3d1cc1cc41dfd30d0ace9e1dc26baf3cf303ced)
@@ -4685,4 +4685,23 @@
 }
 
+@article{Ganzinger80,
+	contributer = {a3moss@uwaterloo.ca},
+	author = {Ganzinger, Harald and Ripken, Knut},
+	title = {Operator Identification in {ADA}: Formal Specification, Complexity, and Concrete Implementation},
+	journal = {SIGPLAN Notices},
+	issue_date = {February 1980},
+	volume = {15},
+	number = {2},
+	month = feb,
+	year = {1980},
+	issn = {0362-1340},
+	pages = {30--42},
+	numpages = {13},
+	url = {http://doi.acm.org/10.1145/947586.947589},
+	doi = {10.1145/947586.947589},
+	publisher = {ACM},
+	address = {New York, NY, USA}
+}
+
 @article{Ford82,
     keywords	= {},