Commons: GNU Free Documentation License
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Version 1.2, November 2002
Copyright (C) 2000,2001,2002  Free Software Foundation, Inc.
51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
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
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.
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
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
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
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.
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.
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.
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.
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
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
M. Delete any section Entitled "Endorsements". Such a section may
not be included in the Modified
N. Do not retitle any existing section to be Entitled "Endorsements"
or to conflict in title with any Invariant
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
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
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
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
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."
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.
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
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.
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.
You may not copy, modify, sublicense, or distribute the Document
except as expressly provided for under this
License. Any other attempt to copy, modify, sublicense or distribute
the Document is void, and will
automatically terminate your rights under this License. However,
parties who have received copies, or rights,
from you under this License will not have their licenses terminated
so long as such parties remain in full
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
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.
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