diff --git a/bibtexbrowser.php b/bibtexbrowser.php
old mode 100644
new mode 100755
index 991e590..e043ccb
--- a/bibtexbrowser.php
+++ b/bibtexbrowser.php
@@ -1379,7 +1379,7 @@ class BibEntry {
 
     // referrer, the id pf a collection of objects
     // see also http://www.openurl.info/registry/docs/pdf/info-sid.pdf    
-    $url_parts[]='rfr_id='.s3988('info:sid/'.$_SERVER['HTTP_HOST'].':'.@$_GET[Q_FILE]);
+    $url_parts[]='rfr_id='.s3988('info:sid/'.@$_SERVER['HTTP_HOST'].':'.@$_GET[Q_FILE]);
 
     $url_parts[]='rft.date='.s3988($this->getYear());