diff -r c71923e6fa2f -r a53762d61c06 server/src/app/Libraries/Utils.php
--- a/server/src/app/Libraries/Utils.php	Fri Feb 03 13:01:08 2017 +0100
+++ b/server/src/app/Libraries/Utils.php	Fri Feb 03 16:35:09 2017 +0100
@@ -11,6 +11,10 @@
  */
 class Utils {
 
+    const SUBJECT_TYPE_BNF   = 'bnf';
+    const SUBJECT_TYPE_LEXVO = 'lxv';
+    const SUBJECT_TYPE_OLAC  = 'olac';
+    const SUBJECT_TYPE_TXT   = 'txt';
 
     /**
      * convert DateIntervals to milliseconds