Fix reference

Author: rayosborn

base_classes/NXparameters.nxdl.xml

@@ -34,10 +34,10 @@
         case is to store the results of optimizing parameters, for
         example, by least-squares fitting, so a number of attributes
         have been defined for this purpose. Normally, this group will be
-        stored in a :ref:NXprocess group, which defines the program used
-        to process these parameters. If multiple functions are used to
-        analyze the data, there can be additional NXparameter groups for
-        each one.        
+        stored in a :ref:`NXprocess group`, which defines the program
+        used to process these parameters. If multiple functions are used
+        to analyze the data, there can be additional NXparameter groups
+        for each one.        
     </doc>
     <attribute name="model">
         <doc>