urlbst -- add @webpage entry and url/doi/eprint/pubmed fields to BibTeX
=======================================================================

Version 0.8, 2019 July 1.

The urlbst package consists of a Perl script which edits BibTeX style
files (.bst) to add a `@webpage` entry type, and which adds a few new
fields -- notably including 'url' -- to all other entry types.  The
distribution includes preconverted versions of the four standard
BibTeX .bst style files.

It has a different goal from Patrick Daly's 'custom-bib' package --
that is intended to create a BibTeX style .bst file from scratch, and
supports 'url' and 'eprint' fields.  This package, on the other hand,
is intended for the case where you already have a style file that
works (or at least, which you cannot or will not change), and edits it
to add the new `@webpage` entry type, plus the new fields.

The added fields are:

  * 'url' and 'lastchecked', to associate a URL with a reference,
    along with the date at which the URL was last checked to exist; 
  * 'doi', for a reference's DOI (see https://doi.org);
  * 'eprint', for an arXiv eprint reference (see http://arxiv.org); and
  * 'pubmed' for a reference's PubMed identifier (PMID, see http://pubmed.gov).

Licences
--------

The copyright and licence position for the modified `.bst` files seems
slightly muddy to me.  On the grounds that any licence is better than
no licence, I therefore assert that the _modifications_ which the
`urlbst` program makes to these files are copyright 2002-03, 2005-12, 2014, 2019,
Norman Gray, and that these modifications are available for
distribution under the terms of the LaTeX Project Public Licence.

The original `.bst` files are copyright Howard Trickey and Oren
Patashnik, with a set of permissions, in text at the top of the files,
which state that "Unlimited copying and redistribution of this file
are permitted as long as it is unmodified" (see the files for the
complete text).  The distribution terms above therefore appear to be
compatible with -- in the sense of being morally equivalent to --
these terms in the `.bst` file.  If anyone disagrees with the logic
here, I'd be very happy to discuss that.

The `urlbst` script itself is distributed under the GPL, version 2.0.

See the files `LICENCE-lppl.txt` and `LICENCE-gpl-2.0.txt` in the
distribution, for the relevant licence text.


Norman Gray  
http://nxg.me.uk
