This plplot docbook documentation project started as a joint effort by
Alan W. Irwin and Rafael Laboissiere to convert the plplot latexinfo
documentation (last modified in 1995 or earlier) to the DocBook SGML
format.  We finished the conversion project in July 1999 and
subsequently we and others have constantly updated our DocBook source
code (see the results from "git log doc/docbook") and the
DocBook-related parts of our build system (see the results from "git
log cmake/modules/docbook.cmake") to improve the substance of our
documentation as well as how it is built.  In addition, we have moved
to the DocBook XML format and using modern DocBook tools to generate
our documentation in various formats (i.e.,
doc/docbook/bin/api2man.pl(.in) to generate the man page form of our
documentation [limited to just our public API documented in
doc/docbook/src/api.xml]; doc/docbook/bin/info-clean.pl,
db2x_xsltproc, db2x_texixml, and makeinfo to generate the info page
form of our full documentation; xmlto to generate the html form of our
full documentation, and "dblatex --backend=xetex" to generate the PDF
form of our full documentation).  To get the latest DocBook
documentation results either build it (for instructions see
plplot/doc/docbook/README.developers) from the latest git master
branch of PLplot or visit http://plplot.org/documentation.php which
points to recent DocBook results in html, pdf, info and man forms.