--- jakarta-poi-original/src/java/org/apache/poi/hssf/model/FormulaParser.java	2003-07-16 20:00:46.000000000 -0500
+++ jakarta-poi-original/src/java/org/apache/poi/hssf/model/FormulaParser.java	2003-07-16 20:05:59.000000000 -0500
@@ -891,7 +891,9 @@ 
      */
     public String toString() {
         SheetReferences refs = null;
-        if (book!=null)  book.getSheetReferences();
+        if (book!=null)  {
+            refs = book.getSheetReferences();
+        }
         StringBuffer buf = new StringBuffer();
            for (int i=0;i<tokens.size();i++) {
             buf.append( ( (Ptg)tokens.get(i)).toFormulaString(refs));