The XML DocType Tag

Version 1:

<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
          "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd">
         

Version 2:

<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
          "/usr/share/xml/docbook/xml-dtd-4.1.2/docbookx.dtd">
         

Version 3:

<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
          "urn:x-oasis:docbook-xml-v4.1.2">