gfdl − GNU Free Documentation License

     GNU Free Documentation License

     Version 1.2, November 2002

             Copyright (c) 2000,2001,2002 Free Software Foundation, Inc.
        59 Temple Place, Suite 330, Boston, MA  02111‐1307, 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 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.


    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

    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, @acronym{SGML} or
    @acronym{XML} using a publicly available @acronym{DTD},
    and standard‐conforming simple @acronym{HTML},
    PostScript or @acronym{PDF} designed for human
    modification.  Examples of transparent image formats
    include @acronym{PNG}, @acronym{XCF} and @acronym{JPG}.
    Opaque formats include proprietary formats that can be
    read and edited only by proprietary word processors,
    @acronym{SGML} or @acronym{XML} for which the
    @acronym{DTD} and/or processing tools are not generally
    available, and the machine‐generated @acronym{HTML},
    PostScript or @acronym{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

    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

    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

    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

    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

    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.


    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.’’


    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


    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 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.


    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 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 Document is Entitled
    ‘‘Acknowledgements’’, ‘‘Dedications’’, or ‘‘History’’,
    the requirement (section 4) to Preserve its Title
    (section 1) will typically require changing the actual


    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

     ADDENDUM: How to use this License for your documents

     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

               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 1.2
          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

                 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

gpl(7), fsf−funding(7).

Copyright (c) 2000 Free Software Foundation, Inc.  59 Temple
Place, Suite 330, Boston, MA  02111−1307, USA

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