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+'chem' is a 'roff' language to generate chemical structure diagrams.
+'@g@chem' is a 'groff' preprocessor that produces output suitable for
+the '@g@pic' preprocessor.
+
+The original version of 'chem' is an 'awk' script written by Brian
+Kernighan <http://cm.bell-labs.com/cm/cs/who/bwk/index.html>.  The
+source files of the 'awk' version of 'chem' are available at
+<http://cm.bell-labs.com/netlib/typesetting/chem.gz>.
+
+This project is a rewrite of 'chem' in Perl for the GNU 'roff' project
+'groff'.  It was written under Perl v5.8.8, but at least Perl v5.6 is
+needed to run the Perl version of 'chem'.
+
+In comparison to the original 'awk' version of 'chem', the Perl
+version does the following changements:
+- the options -h, --help, -v, --version to output usage and version
+information are added.
+- remove some functions 'inline', 'shiftfields', and 'set' and some
+variables that are used only once.
+
+The subdirectory 'examples/' contains example files for chem.  They
+are written in the 'chem' language.  The file names end with .chem.
+
+
+####### License
+
+Copyright (C) 2006-2020 Free Software Foundation, Inc.
+Written by Bernd Warken <groff-bernd.warken-72@web.de>.
+
+This file is part of 'chem', which is part of 'groff'.
+
+'groff' is free software; you can redistribute it and/or modify it
+under the terms of the GNU General Public License (GPL) version 2 as
+published by the Free Software Foundation.
+
+'groff' is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+The GPL2 license text is available in the internet at
+<http://www.gnu.org/licenses/gpl-2.0.html>.
+
+
+##### Editor settings
+Local Variables:
+fill-column: 72
+mode: text
+End:
+vim: set textwidth=72: