diff --git a/docs/pdf/intro.tex b/docs/pdf/intro.tex
index b55b6629..fd8ea73a 100644
--- a/docs/pdf/intro.tex
+++ b/docs/pdf/intro.tex
@@ -138,7 +138,7 @@ are classified as:
 
 The main underlying principle of the PSBLAS library is that the
 library objects are created and exist with reference to a discretized
-space to which there corresponds and index space and a matrix sparsity
+space to which there corresponds an index space and a matrix sparsity
 pattern. As an example, consider a cell-centered finite-volume
 discretization of  the Navier-Stokes equations on a simulation domain;
 the index space $1\dots n$ is isomorphic to the set of cell centers,