0.6
. add sgml-register-catalog - Add catalog statement to the so called
  supercatalog (SGML Open Catalog format).

0.5
. parse-sgml-catalog.sh - Print normalized SGML catalog files.
. sgml2xmlcat.sh - Convert a normalized SGML catalog to an XML catalog.

0.2
. install-dtd.sh:
  - Recognize ISO identifiers.
  - Handle language and version.
  - Error checking.

0.1
. install-dtd.sh: Bash script to parse PUBLIC identifiers.