This is the "Smart Solidity" book viewable on gitbook.
GNU Free Documentation License 1.3
Copyright (C) 2016 Ramesh Nair.
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;
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A copy of the license is included in the section entitled "License".