crossrefenum/doc/LICENSE_FDL_1-3.md

## GNU Free Documentation License {#gnu-free-documentation-license-1}

Version 1.3, 3 November 2008

Copyright © 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
\<<https://fsf.org/>\>

Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.

### 0. PREAMBLE {#section0}

The purpose of this License is to make a manual, textbook, or other
functional and useful document \"free\" in the sense of freedom: to
assure everyone the effective freedom to copy and redistribute it, with
or without modifying it, either commercially or noncommercially.
Secondarily, this License preserves for the author and publisher a way
to get credit for their work, while not being considered responsible for
modifications made by others.

This License is a kind of \"copyleft\", which means that derivative
works of the document must themselves be free in the same sense. It
complements the GNU General Public License, which is a copyleft license
designed for free software.

We have designed this License in order to use it for manuals for free
software, because free software needs free documentation: a free program
should come with manuals providing the same freedoms that the software
does. But this License is not limited to software manuals; it can be
used for any textual work, regardless of subject matter or whether it is
published as a printed book. We recommend this License principally for
works whose purpose is instruction or reference.

### 1. APPLICABILITY AND DEFINITIONS {#section1}

This License applies to any manual or other work, in any medium, that
contains a notice placed by the copyright holder saying it can be
distributed under the terms of this License. Such a notice grants a
world-wide, royalty-free license, unlimited in duration, to use that
work under the conditions stated herein. The \"Document\", below, refers
to any such manual or work. Any member of the public is a licensee, and
is addressed as \"you\". You accept the license if you copy, modify or
distribute the work in a way requiring permission under copyright law.

A \"Modified Version\" of the Document means any work containing the
Document or a portion of it, either copied verbatim, or with
modifications and/or translated into another language.

A \"Secondary Section\" is a named appendix or a front-matter section of
the Document that deals exclusively with the relationship of the
publishers or authors of the Document to the Document\'s overall subject
(or to related matters) and contains nothing that could fall directly
within that overall subject. (Thus, if the Document is in part a
textbook of mathematics, a Secondary Section may not explain any
mathematics.) The relationship could be a matter of historical
connection with the subject or with related matters, or of legal,
commercial, philosophical, ethical or political position regarding them.

The \"Invariant Sections\" are certain Secondary Sections whose titles
are designated, as being those of Invariant Sections, in the notice that
says that the Document is released under this License. If a section does
not fit the above definition of Secondary then it is not allowed to be
designated as Invariant. The Document may contain zero Invariant
Sections. If the Document does not identify any Invariant Sections then
there are none.

The \"Cover Texts\" are certain short passages of text that are listed,
as Front-Cover Texts or Back-Cover Texts, in the notice that says that
the Document is released under this License. A Front-Cover Text may be
at most 5 words, and a Back-Cover Text may be at most 25 words.

A \"Transparent\" copy of the Document means a machine-readable copy,
represented in a format whose specification is available to the general
public, that is suitable for revising the document straightforwardly
with generic text editors or (for images composed of pixels) generic
paint programs or (for drawings) some widely available drawing editor,
and that is suitable for input to text formatters or for automatic
translation to a variety of formats suitable for input to text
formatters. A copy made in an otherwise Transparent file format whose
markup, or absence of markup, has been arranged to thwart or discourage
subsequent modification by readers is not Transparent. An image format
is not Transparent if used for any substantial amount of text. A copy
that is not \"Transparent\" is called \"Opaque\".

Examples of suitable formats for Transparent copies include plain ASCII
without markup, Texinfo input format, LaTeX input format, SGML or XML
using a publicly available DTD, and standard-conforming simple HTML,
PostScript or PDF designed for human modification. Examples of
transparent image formats include PNG, XCF and JPG. Opaque formats
include proprietary formats that can be read and edited only by
proprietary word processors, SGML or XML for which the DTD and/or
processing tools are not generally available, and the machine-generated
HTML, PostScript or PDF produced by some word processors for output
purposes only.

The \"Title Page\" means, for a printed book, the title page itself,
plus such following pages as are needed to hold, legibly, the material
this License requires to appear in the title page. For works in formats
which do not have any title page as such, \"Title Page\" means the text
near the most prominent appearance of the work\'s title, preceding the
beginning of the body of the text.

The \"publisher\" means any person or entity that distributes copies of
the Document to the public.

A section \"Entitled XYZ\" means a named subunit of the Document whose
title either is precisely XYZ or contains XYZ in parentheses following
text that translates XYZ in another language. (Here XYZ stands for a
specific section name mentioned below, such as \"Acknowledgements\",
\"Dedications\", \"Endorsements\", or \"History\".) To \"Preserve the
Title\" of such a section when you modify the Document means that it
remains a section \"Entitled XYZ\" according to this definition.

The Document may include Warranty Disclaimers next to the notice which
states that this License applies to the Document. These Warranty
Disclaimers are considered to be included by reference in this License,
but only as regards disclaiming warranties: any other implication that
these Warranty Disclaimers may have is void and has no effect on the
meaning of this License.

### 2. VERBATIM COPYING {#section2}

You may copy and distribute the Document in any medium, either
commercially or noncommercially, provided that this License, the
copyright notices, and the license notice saying this License applies to
the Document are reproduced in all copies, and that you add no other
conditions whatsoever to those of this License. You may not use
technical measures to obstruct or control the reading or further copying
of the copies you make or distribute. However, you may accept
compensation in exchange for copies. If you distribute a large enough
number of copies you must also follow the conditions in section 3.

You may also lend copies, under the same conditions stated above, and
you may publicly display copies.

### 3. COPYING IN QUANTITY {#section3}

If you publish printed copies (or copies in media that commonly have
printed covers) of the Document, numbering more than 100, and the
Document\'s license notice requires Cover Texts, you must enclose the
copies in covers that carry, clearly and legibly, all these Cover Texts:
Front-Cover Texts on the front cover, and Back-Cover Texts on the back
cover. Both covers must also clearly and legibly identify you as the
publisher of these copies. The front cover must present the full title
with all words of the title equally prominent and visible. You may add
other material on the covers in addition. Copying with changes limited
to the covers, as long as they preserve the title of the Document and
satisfy these conditions, can be treated as verbatim copying in other
respects.

If the required texts for either cover are too voluminous to fit
legibly, you should put the first ones listed (as many as fit
reasonably) on the actual cover, and continue the rest onto adjacent
pages.

If you publish or distribute Opaque copies of the Document numbering
more than 100, you must either include a machine-readable Transparent
copy along with each Opaque copy, or state in or with each Opaque copy a
computer-network location from which the general network-using public
has access to download using public-standard network protocols a
complete Transparent copy of the Document, free of added material. If
you use the latter option, you must take reasonably prudent steps, when
you begin distribution of Opaque copies in quantity, to ensure that this
Transparent copy will remain thus accessible at the stated location
until at least one year after the last time you distribute an Opaque
copy (directly or through your agents or retailers) of that edition to
the public.

It is requested, but not required, that you contact the authors of the
Document well before redistributing any large number of copies, to give
them a chance to provide you with an updated version of the Document.

### 4. MODIFICATIONS {#section4}

You may copy and distribute a Modified Version of the Document under the
conditions of sections 2 and 3 above, provided that you release the
Modified Version under precisely this License, with the Modified Version
filling the role of the Document, thus licensing distribution and
modification of the Modified Version to whoever possesses a copy of it.
In addition, you must do these things in the Modified Version:

-   A. Use in the Title Page (and on the covers, if any) a title
    distinct from that of the Document, and from those of previous
    versions (which should, if there were any, be listed in the History
    section of the Document). You may use the same title as a previous
    version if the original publisher of that version gives permission.
-   B. List on the Title Page, as authors, one or more persons or
    entities responsible for authorship of the modifications in the
    Modified Version, together with at least five of the principal
    authors of the Document (all of its principal authors, if it has
    fewer than five), unless they release you from this requirement.
-   C. State on the Title page the name of the publisher of the Modified
    Version, as the publisher.
-   D. Preserve all the copyright notices of the Document.
-   E. Add an appropriate copyright notice for your modifications
    adjacent to the other copyright notices.
-   F. Include, immediately after the copyright notices, a license
    notice giving the public permission to use the Modified Version
    under the terms of this License, in the form shown in the Addendum
    below.
-   G. Preserve in that license notice the full lists of Invariant
    Sections and required Cover Texts given in the Document\'s license
    notice.
-   H. Include an unaltered copy of this License.
-   I. Preserve the section Entitled \"History\", Preserve its Title,
    and add to it an item stating at least the title, year, new authors,
    and publisher of the Modified Version as given on the Title Page. If
    there is no section Entitled \"History\" in the Document, create one
    stating the title, year, authors, and publisher of the Document as
    given on its Title Page, then add an item describing the Modified
    Version as stated in the previous sentence.
-   J. Preserve the network location, if any, given in the Document for
    public access to a Transparent copy of the Document, and likewise
    the network locations given in the Document for previous versions it
    was based on. These may be placed in the \"History\" section. You
    may omit a network location for a work that was published at least
    four years before the Document itself, or if the original publisher
    of the version it refers to gives permission.
-   K. For any section Entitled \"Acknowledgements\" or \"Dedications\",
    Preserve the Title of the section, and preserve in the section all
    the substance and tone of each of the contributor acknowledgements
    and/or dedications given therein.
-   L. Preserve all the Invariant Sections of the Document, unaltered in
    their text and in their titles. Section numbers or the equivalent
    are not considered part of the section titles.
-   M. Delete any section Entitled \"Endorsements\". Such a section may
    not be included in the Modified Version.
-   N. Do not retitle any existing section to be Entitled
    \"Endorsements\" or to conflict in title with any Invariant Section.
-   O. Preserve any Warranty Disclaimers.

If the Modified Version includes new front-matter sections or appendices
that qualify as Secondary Sections and contain no material copied from
the Document, you may at your option designate some or all of these
sections as invariant. To do this, add their titles to the list of
Invariant Sections in the Modified Version\'s license notice. These
titles must be distinct from any other section titles.

You may add a section Entitled \"Endorsements\", provided it contains
nothing but endorsements of your Modified Version by various
parties---for example, statements of peer review or that the text has
been approved by an organization as the authoritative definition of a
standard.

You may add a passage of up to five words as a Front-Cover Text, and a
passage of up to 25 words as a Back-Cover Text, to the end of the list
of Cover Texts in the Modified Version. Only one passage of Front-Cover
Text and one of Back-Cover Text may be added by (or through arrangements
made by) any one entity. If the Document already includes a cover text
for the same cover, previously added by you or by arrangement made by
the same entity you are acting on behalf of, you may not add another;
but you may replace the old one, on explicit permission from the
previous publisher that added the old one.

The author(s) and publisher(s) of the Document do not by this License
give permission to use their names for publicity for or to assert or
imply endorsement of any Modified Version.

### 5. COMBINING DOCUMENTS {#section5}

You may combine the Document with other documents released under this
License, under the terms defined in section 4 above for modified
versions, provided that you include in the combination all of the
Invariant Sections of all of the original documents, unmodified, and
list them all as Invariant Sections of your combined work in its license
notice, and that you preserve all their Warranty Disclaimers.

The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single
copy. If there are multiple Invariant Sections with the same name but
different contents, make the title of each such section unique by adding
at the end of it, in parentheses, the name of the original author or
publisher of that section if known, or else a unique number. Make the
same adjustment to the section titles in the list of Invariant Sections
in the license notice of the combined work.

In the combination, you must combine any sections Entitled \"History\"
in the various original documents, forming one section Entitled
\"History\"; likewise combine any sections Entitled
\"Acknowledgements\", and any sections Entitled \"Dedications\". You
must delete all sections Entitled \"Endorsements\".

### 6. COLLECTIONS OF DOCUMENTS {#section6}

You may make a collection consisting of the Document and other documents
released under this License, and replace the individual copies of this
License in the various documents with a single copy that is included in
the collection, provided that you follow the rules of this License for
verbatim copying of each of the documents in all other respects.

You may extract a single document from such a collection, and distribute
it individually under this License, provided you insert a copy of this
License into the extracted document, and follow this License in all
other respects regarding verbatim copying of that document.

### 7. AGGREGATION WITH INDEPENDENT WORKS {#section7}

A compilation of the Document or its derivatives with other separate and
independent documents or works, in or on a volume of a storage or
distribution medium, is called an \"aggregate\" if the copyright
resulting from the compilation is not used to limit the legal rights of
the compilation\'s users beyond what the individual works permit. When
the Document is included in an aggregate, this License does not apply to
the other works in the aggregate which are not themselves derivative
works of the Document.

If the Cover Text requirement of section 3 is applicable to these copies
of the Document, then if the Document is less than one half of the
entire aggregate, the Document\'s Cover Texts may be placed on covers
that bracket the Document within the aggregate, or the electronic
equivalent of covers if the Document is in electronic form. Otherwise
they must appear on printed covers that bracket the whole aggregate.

### 8. TRANSLATION {#section8}

Translation is considered a kind of modification, so you may distribute
translations of the Document under the terms of section 4. Replacing
Invariant Sections with translations requires special permission from
their copyright holders, but you may include translations of some or all
Invariant Sections in addition to the original versions of these
Invariant Sections. You may include a translation of this License, and
all the license notices in the Document, and any Warranty Disclaimers,
provided that you also include the original English version of this
License and the original versions of those notices and disclaimers. In
case of a disagreement between the translation and the original version
of this License or a notice or disclaimer, the original version will
prevail.

If a section in the Document is Entitled \"Acknowledgements\",
\"Dedications\", or \"History\", the requirement (section 4) to Preserve
its Title (section 1) will typically require changing the actual title.

### 9. TERMINATION {#section9}

You may not copy, modify, sublicense, or distribute the Document except
as expressly provided under this License. Any attempt otherwise to copy,
modify, sublicense, or distribute it is void, and will automatically
terminate your rights under this License.

However, if you cease all violation of this License, then your license
from a particular copyright holder is reinstated (a) provisionally,
unless and until the copyright holder explicitly and finally terminates
your license, and (b) permanently, if the copyright holder fails to
notify you of the violation by some reasonable means prior to 60 days
after the cessation.

Moreover, your license from a particular copyright holder is reinstated
permanently if the copyright holder notifies you of the violation by
some reasonable means, this is the first time you have received notice
of violation of this License (for any work) from that copyright holder,
and you cure the violation prior to 30 days after your receipt of the
notice.

Termination of your rights under this section does not terminate the
licenses of parties who have received copies or rights from you under
this License. If your rights have been terminated and not permanently
reinstated, receipt of a copy of some or all of the same material does
not give you any rights to use it.

### 10. FUTURE REVISIONS OF THIS LICENSE {#section10}

The Free Software Foundation may publish new, revised versions of the
GNU Free Documentation License from time to time. Such new versions will
be similar in spirit to the present version, but may differ in detail to
address new problems or concerns. See <https://www.gnu.org/licenses/>.

Each version of the License is given a distinguishing version number. If
the Document specifies that a particular numbered version of this
License \"or any later version\" applies to it, you have the option of
following the terms and conditions either of that specified version or
of any later version that has been published (not as a draft) by the
Free Software Foundation. If the Document does not specify a version
number of this License, you may choose any version ever published (not
as a draft) by the Free Software Foundation. If the Document specifies
that a proxy can decide which future versions of this License can be
used, that proxy\'s public statement of acceptance of a version
permanently authorizes you to choose that version for the Document.

### 11. RELICENSING {#section11}

\"Massive Multiauthor Collaboration Site\" (or \"MMC Site\") means any
World Wide Web server that publishes copyrightable works and also
provides prominent facilities for anybody to edit those works. A public
wiki that anybody can edit is an example of such a server. A \"Massive
Multiauthor Collaboration\" (or \"MMC\") contained in the site means any
set of copyrightable works thus published on the MMC site.

\"CC-BY-SA\" means the Creative Commons Attribution-Share Alike 3.0
license published by Creative Commons Corporation, a not-for-profit
corporation with a principal place of business in San Francisco,
California, as well as future copyleft versions of that license
published by that same organization.

\"Incorporate\" means to publish or republish a Document, in whole or in
part, as part of another Document.

An MMC is \"eligible for relicensing\" if it is licensed under this
License, and if all works that were first published under this License
somewhere other than this MMC, and subsequently incorporated in whole or
in part into the MMC, (1) had no cover texts or invariant sections, and
(2) were thus incorporated prior to November 1, 2008.

The operator of an MMC Site may republish an MMC contained in the site
under CC-BY-SA on the same site at any time before August 1, 2009,
provided the MMC is eligible for relicensing.

## ADDENDUM: How to use this License for your documents {#addendum}

To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and license
notices just after the title page:

        Copyright (C)  YEAR  YOUR NAME.
        Permission is granted to copy, distribute and/or modify this document
        under the terms of the GNU Free Documentation License, Version 1.3
        or any later version published by the Free Software Foundation;
        with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
        A copy of the license is included in the section entitled "GNU
        Free Documentation License".

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
replace the \"with ... Texts.\" line with this:

        with the Invariant Sections being LIST THEIR TITLES, with the
        Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.

If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.

If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of free
software license, such as the GNU General Public License, to permit
their use in free software.