/usr/share/gtkmathview/gtkmathview.conf.dtd is in libgtkmathview0c2a 0.8.0-10+nmu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 | <?xml version="1.0" encoding="iso8859-1"?>
<!ELEMENT math-engine-configuration (key|section)*>
<!ELEMENT section (section|key)*>
<!ATTLIST section name NMTOKEN #REQUIRED>
<!ELEMENT key (#PCDATA)>
<!ATTLIST key name NMTOKEN #REQUIRED>
|