Fix typo in doc

Author: Florian360

doc/SparseQuickReference.dox

@@ -244,7 +244,7 @@ As stated earlier, for a read-write sub-matrix (RW), the evaluation can be done
 <td>
 \code
 sm1.valuePtr();      // Pointer to the values
-sm1.innerIndextr();  // Pointer to the indices.
+sm1.innerIndexPtr();  // Pointer to the indices.
 sm1.outerIndexPtr(); // Pointer to the beginning of each inner vector
 \endcode
 </td>