https://creativecommons.org/licenses/by/3.0/ 
Creative Commons Attribution 3.0 Unported (CC BY 3.0) 
This is a human-readable summary of (and not a substitute for) the license:
https://creativecommons.org/licenses/by/3.0/legalcode
YOU ARE FREE TO:: 
Share — copy and redistribute the material in any medium or format 
Adapt — remix, transform, and build upon the material for any purpose, even
commercially.
The licensor cannot revoke these freedoms as long as you follow the license
terms.
UNDER THE FOLLOWING TERMS: 
Attribution — You must give appropriate credit, provide a link to the license,
and indicate if changes were made. You may do so in any reasonable manner, but
not in any way that suggests the licensor endorses you or your use.
No additional restrictions — You may not apply legal terms or technological
measures that legally restrict others from doing anything the license permits.
Notices: You do not have to comply with the license for elements of the material
in the public domain or where your use is permitted by an applicable exception
or limitation. No warranties are given. The license may not give you all of the
permissions necessary for your intended use. For example, other rights such as
publicity, privacy, or moral rights may limit how you use the material.