--- a/text/ncat.tex	Fri Jan 07 09:08:15 2011 -0800
+++ b/text/ncat.tex	Fri Jan 07 12:41:45 2011 -0800
@@ -35,7 +35,7 @@
 Other definitions have a separate set of 1-morphisms for each interval $[0,l] \sub \r$, 
 a separate set of 2-morphisms for each rectangle $[0,l_1]\times [0,l_2] \sub \r^2$,
 and so on.
-(This allows for strict associativity.)
+(This allows for strict associativity; see \cite{ulrike-tillmann-2008,0909.2212}.)
 Still other definitions (see, for example, \cite{MR2094071})
 model the $k$-morphisms on more complicated combinatorial polyhedra.