\noindent\copyright~2013 Dmitri V. Fedorov

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\noindent Permission is granted to copy and redistribute this
work under the terms of either the {GNU General Public
License}\footnote{http://en.wikipedia.org/wiki/GPL},
version 3 or later, as published by the Free Software
Foundation, or the {Creative Commons Attribution Share Alike
License}\footnote{http://en.wikipedia.org/wiki/CC-BY-SA}, version 3 or
later, as published by the Creative Commons corporation.

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\noindent This work is distributed in the hope that it will be useful, but
without any warranty. No responsibility is assumed by the author and the
publisher for any damage from any use of any methods, instructions or
ideas contained in the material herein.
