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GNU Free Documentation License

Discussion Draft 1 of Version 2, 25 September 2006


Copyright (C) 2000, 2002, 2006 Free Software Foundation, Inc.
51 Franklin Street, 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 work of authorship free. This means giving all users the four essential freedoms:

0. The freedom to read, view, or use the work. 1. The freedom to change the work, with access to formats which make that convenient to do. 2. The freedom to make and redistribute copies of the work. 3. The freedom to distribute modified versions.

Secondarily, this License assures the author and publisher the credit for their work, while sparing them any appearance of being 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.

This License is not limited to "documentation", or even to works that are textual; it can be used for any work of authorship meant for human appreciation, rather than machine execution. We recommend this License principally for works whose purpose is instruction or reference, but it can be used for any work regardless of the subject matter, even for art and fiction. The only kind of work for which this should not be used is software.


In this License, each licensee is addressed as "you," while "the Work" refers to any work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. It may physically consist of multiple volumes. A "modified" work includes versions that have been translated, transformed, or adapted, or to which material has been added. A work "based on" another work means any modified version for which permission is necessary under applicable copyright law.

To "propagate" a work means doing anything with it that requires permission under applicable copyright law, except making modifications that you do not share. Propagation includes copying, distribution (with or without modification), making available or communicating to the public,publicly displaying or performing the work and in some countries other activities as well. To "convey" a work means any kind of propagation that enables other parties to make or receive copies, excluding sublicensing.

An "Ancillary Section" is a named section preceding or following the main body of the Work that deals exclusively with the relationship of the publishers or authors of the Work to the Work's overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (Thus, if the Work is in part a textbook of mathematics, an Ancillary 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 Ancillary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Work is released under this License. If a section does not fit the above definition of Ancillary then it is not allowed to be designated as Invariant. The Work may contain zero Invariant Sections. If the Work 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 Work 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 Work means a machine-readable copy, represented in a format whose specification is available to the general public, that is suitable for revision straightforwardly by generic editors appropriate to the medium (text, sound, video, etc.), and that is suitable (perhaps through programmed format conversion) for input to a wide variety of programs for processing that medium. Material stored in an otherwise Transparent file format in a way that thwarts or discourages subsequent substantial modification by others is not Transparent. A copy that is not "Transparent" is called "Opaque".

Examples of suitable formats for Transparent copies of textual works include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD or schema, OpenDocument format, and standard-conforming simple HTML, PostScript or PDF designed for human modification. Examples of transparent image formats include PNG, XCF and JPG. Examples of transparent video formats include MPEG2 and Ogg Theora. Opaque formats include proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD, schema 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 the portion of the work where information such as title, authors, date of publication, and copyright notice would normally appear.

A section "Entitled XYZ" means a named section of the Work 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 Work means that it remains a section "Entitled XYZ" according to this definition.

The Work may include Warranty Disclaimers next to the notice which states that this License applies to the Work. 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 have a world-wide, royalty-free license, for the duration of the copyright on the Work, to use the Work under the conditions stated herein. You accept the license if you propagate the Work.


You may propagate the Work unmodified in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Work are reproduced in all copies, and that you add no other conditions whatsoever to those of this License.

You need not include a copy of this License in the Work if you have registered the work's license with a national agency that maintains a network server through which the general public can find out its license.

You may not apply technical measures to obstruct or control the use or further copying of any copies you make or distribute, by those to whom they may be distributed. However, you may charge a fee in exchange for copies. You may transmit copies with methods that give you legal rights to control further use, copying or transmission, only on condition that you waive the use of those legal rights to impose any conditions aside from those of this License.

You may publically perform the Work provided you make a transparent copy available as described in section 3 as though you had propagated opaque copies to the audience.


If you publish printed copies (or copies in media that commonly have printed covers) of the Work, numbering more than 100, and the Work'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 clearly and unambiguously present the full title. Copying with changes limited to the covers, under 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 convey Opaque copies of the Work numbering more than 100, you must also convey a corresponding machine-readable Transparent version. The Transparent version need not have identical formatting as long as its contents are the same and are clearly visible, and non-textual contents have equal or superior resolution and quality. When you convey the Opaque copies by offering access to copy from a designated place, you must offer equivalent access to copy the Transparent version from the same place. Otherwise, you must convey 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 anonymous gratis access to download, using public-standard network protocols, a corresponding Transparent copy of the Work. Under the latter option, you must take reasonably prudent steps, when you begin conveying 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 convey 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 Work well before conveying any large number of copies, to give them a chance to provide you with an updated version of the Work.


You may convey a Modified Version of the Work 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 Work, 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 Work, and from those of previous versions as listed in the History section.
B. List as authors (on the Title Page, if any), one or more persons or entities responsible for authorship of the modifications in the Modified Version.
C. Credit (on the Title Page, if any) at least five of the principal authors of the Work (all of them, if it has fewer than five) if the material derived from the Work is more than 1/4 of the total.
D. Prominently state the name of the publisher of the Modified Version.
E. Preserve all the copyright notices of the Work.
F. Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.
G. 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.
H. Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Work's license notice.
I. Include an unaltered copy of this License.
J. 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. If there is no section Entitled "History" in the Work, create one stating the title, year, authors, and publisher of the Work, then add an item describing the Modified Version as stated in the previous sentence.
K. Preserve the network location, if any, given in the Work for public access to a Transparent copy of the Work, and likewise the network locations given in the Work 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 Work itself.
L. 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. Acknowledgments and Dedications can be deleted when a Modified Version deletes all material to which the Acknowledgments and Dedications could reasonably have applied.
M. Preserve all the Invariant Sections of the Work, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.
N. Delete any section Entitled "Endorsements". Such a section may not be included in the Modified Version.
O. Do not retitle any existing section to be Entitled "Endorsements" or to conflict in title with any Invariant Section.
P. Preserve any Warranty Disclaimers.

Authors and publishers of previous versions can release you from above requirements to cite or refer to them or their versions.

If the Modified Version includes Ancillary Sections that contain no material copied from the Work, 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 Work 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 Work do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.


You may combine the Work with other works 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 works, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers. Clause 4C applies to all the principal authors of all the combined works, taken together.

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 a unique number at the end. 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 preserve all warranty disclaimers, combine any sections Entitled "History" in the various original works, 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 Work and other works released under this License, and replace the individual copies of this License in the various works 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 works in all other respects.

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


You may publish a work, a Modified Version, or a collection, of up to 20,000 characters of text (excluding formatting mark-up) in electronic form, or up to 12 normal printed pages, or up to a minute of audio or video, as an Excerpt. An Excerpt follows the applicable rules of this license, except that the following required materials--the copy of this license, title page materials, historical copyright notices, warranty disclaimers, and any required sections--may be replaced by one or more publicly accessible URLs referring to the same materials.


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

If the Cover Text requirement of section 3 is applicable to these copies of the Work, then if the Work is less than one half of the entire aggregate, the Work's Cover Texts may be placed on covers that bracket the Work within the aggregate, or the electronic equivalent of covers if the Work 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 Work 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 Work, and any Warrany 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 Work is Entitled "Acknowledgements", "Dedications", or "History", the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.


If the Work has no Cover Texts and no Invariant Sections then you may relicense the Work under the GNU Simpler Free Documentation License.


If the Work was previously published, with no Cover Texts, no Invariant Sections, and no Acknowledgements or Dedications or Endorsements section, in a system for massive public collaboration under version 1.2 of this License, and if all the material in the Work was either initially developed in that collaboration system or had been imported into it before 1 June 2006, then you may relicense the Work under the GNU Wiki License.]


You may not propagate or modify the Work except as expressly provided for under this License. Any attempt otherwise to do so is void. If you violate this License, any copyright holder may put you on notice by notifying you of the violation, by any reasonable means, provided 60 days have not elapsed since the last violation. Having put you on notice, the copyright holder may then terminate your license at any time. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as they remain in full compliance.


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 Work 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 Work 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.

For instructions on how to use this License, see


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