From article page: "This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited." Also link from article page goes to CC-By page 'Attribution 3.0 Unported (CC BY 3.0)' "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." ---MA 17/1/18