library/ext/sgml is part of SWI-Prolog's home, whose LICENSE at the home's root
states SWI-Prolog's own licence. The files below are under the licence
named above them, whose text follows them; a file's own header, where it
has one, states its grant, and any exception to it, in full.

========================================================================
License: LicenseRef-ISO-8879-entities AND LicenseRef-W3C-document-19971218
Files:
  library/ext/sgml/DTD/HTMLlat1.ent
  library/ext/sgml/DTD/HTMLspec.ent
  library/ext/sgml/DTD/HTMLsym.ent
Copyright:
  Copyright (c) 1986 International Organization for Standardization
  Copyright (c) 1997 World Wide Web Consortium, (Massachusetts Institute of Technology, Institut National de Recherche en Informatique et en Automatique, Keio University)

--- LicenseRef-ISO-8879-entities ---

Portions (C) International Organization for Standardization 1986
Permission to copy in any form is granted for use with
conforming SGML systems and applications as defined in
ISO 8879, provided this notice is included in all copies.

--- LicenseRef-W3C-document-19971218 ---

The copyright notice of the HTML 4.0 Recommendation of 18 December 1997,
https://www.w3.org/TR/REC-html40-971218/about.html#copyright, reads:

Copyright © 1997 World Wide Web Consortium, (Massachusetts Institute of
Technology, Institut National de Recherche en Informatique et en
Automatique, Keio University). All Rights Reserved.

Documents on the W3C site are provided by the copyright holders under the
following license. By obtaining, using and/or copying this document, or the
W3C document from which this statement is linked, you agree that you have
read, understood, and will comply with the following terms and conditions:

Permission to use, copy, and distribute the contents of this document, or
the W3C document from which this statement is linked, in any medium for any
purpose and without fee or royalty is hereby granted, provided that you
include the following on ALL copies of the document, or portions thereof,
that you use:

  1. A link or URI to the original W3C document.
  2. The pre-existing copyright notice of the original author, if it
     doesn't exist, a notice of the form: "Copyright © World Wide Web
     Consortium, (Massachusetts Institute of Technology, Institut National
     de Recherche en Informatique et en Automatique, Keio University). All
     Rights Reserved."
  3. If it exists, the STATUS of the W3C document.

When space permits, inclusion of the full text of this NOTICE should be
provided. In addition, credit shall be attributed to the copyright holders
for any software, documents, or other items or products that you create
pursuant to the implementation of the contents of this document, or any
portion thereof.

No right to create modifications or derivatives is granted pursuant to this
license.

THIS DOCUMENT IS PROVIDED "AS IS," AND COPYRIGHT HOLDERS MAKE NO
REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED
TO, WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE,
NON-INFRINGEMENT, OR TITLE; THAT THE CONTENTS OF THE DOCUMENT ARE SUITABLE
FOR ANY PURPOSE; NOR THAT THE IMPLEMENTATION OF SUCH CONTENTS WILL NOT
INFRINGE ANY THIRD PARTY PATENTS, COPYRIGHTS, TRADEMARKS OR OTHER RIGHTS.

COPYRIGHT HOLDERS WILL NOT BE LIABLE FOR ANY DIRECT, INDIRECT, SPECIAL OR
CONSEQUENTIAL DAMAGES ARISING OUT OF ANY USE OF THE DOCUMENT OR THE
PERFORMANCE OR IMPLEMENTATION OF THE CONTENTS THEREOF.

The name and trademarks of copyright holders may NOT be used in advertising
or publicity pertaining to this document or its contents without specific,
written prior permission. Title to copyright in this document will at all
times remain with copyright holders.

========================================================================
License: LicenseRef-W3C-document-19971218
Files:
  library/ext/sgml/DTD/HTML4.dcl
  library/ext/sgml/DTD/HTML4.dtd
  library/ext/sgml/DTD/HTML4.soc
Copyright:
  Copyright (c) 1997 World Wide Web Consortium, (Massachusetts Institute of Technology, Institut National de Recherche en Informatique et en Automatique, Keio University)

--- LicenseRef-W3C-document-19971218 ---

The copyright notice of the HTML 4.0 Recommendation of 18 December 1997,
https://www.w3.org/TR/REC-html40-971218/about.html#copyright, reads:

Copyright © 1997 World Wide Web Consortium, (Massachusetts Institute of
Technology, Institut National de Recherche en Informatique et en
Automatique, Keio University). All Rights Reserved.

Documents on the W3C site are provided by the copyright holders under the
following license. By obtaining, using and/or copying this document, or the
W3C document from which this statement is linked, you agree that you have
read, understood, and will comply with the following terms and conditions:

Permission to use, copy, and distribute the contents of this document, or
the W3C document from which this statement is linked, in any medium for any
purpose and without fee or royalty is hereby granted, provided that you
include the following on ALL copies of the document, or portions thereof,
that you use:

  1. A link or URI to the original W3C document.
  2. The pre-existing copyright notice of the original author, if it
     doesn't exist, a notice of the form: "Copyright © World Wide Web
     Consortium, (Massachusetts Institute of Technology, Institut National
     de Recherche en Informatique et en Automatique, Keio University). All
     Rights Reserved."
  3. If it exists, the STATUS of the W3C document.

When space permits, inclusion of the full text of this NOTICE should be
provided. In addition, credit shall be attributed to the copyright holders
for any software, documents, or other items or products that you create
pursuant to the implementation of the contents of this document, or any
portion thereof.

No right to create modifications or derivatives is granted pursuant to this
license.

THIS DOCUMENT IS PROVIDED "AS IS," AND COPYRIGHT HOLDERS MAKE NO
REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED
TO, WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE,
NON-INFRINGEMENT, OR TITLE; THAT THE CONTENTS OF THE DOCUMENT ARE SUITABLE
FOR ANY PURPOSE; NOR THAT THE IMPLEMENTATION OF SUCH CONTENTS WILL NOT
INFRINGE ANY THIRD PARTY PATENTS, COPYRIGHTS, TRADEMARKS OR OTHER RIGHTS.

COPYRIGHT HOLDERS WILL NOT BE LIABLE FOR ANY DIRECT, INDIRECT, SPECIAL OR
CONSEQUENTIAL DAMAGES ARISING OUT OF ANY USE OF THE DOCUMENT OR THE
PERFORMANCE OR IMPLEMENTATION OF THE CONTENTS THEREOF.

The name and trademarks of copyright holders may NOT be used in advertising
or publicity pertaining to this document or its contents without specific,
written prior permission. Title to copyright in this document will at all
times remain with copyright holders.
