commit b5317fb4362306c714623d030f1c187399da2629
Author: Tanmai Khanna <khanna.tanmai@gmail.com>
Date:   Tue Jun 16 21:27:16 2020 +0530

    Update dtd to work with arx files that dont have cat and markables sections

diff --git a/src/anaphora.dtd b/src/anaphora.dtd
index e928f63..5998af8 100644
--- a/src/anaphora.dtd
+++ b/src/anaphora.dtd
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 
-<!ELEMENT ref (section-parameters, section-def-cats, section-markables)>
+<!ELEMENT ref (section-parameters, section-def-cats?, section-markables?)>
 <!--
      'ref' is the root element containing the whole anaphora resolution rule file.
 -->