© 2015 The Authors. This is an open access article under the terms of the <a href="http://creativecommons.org/licenses/by-nc-nd/4.0/" title="Link to external resource: http://creativecommons.org/licenses/by-nc-nd/4.0/">Creative Commons Attribution-NonCommercial-NoDerivs</a> License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
Except where otherwise noted, this item's license is described as © 2015 The Authors. This is an open access article under the terms of the <a href="http://creativecommons.org/licenses/by-nc-nd/4.0/" title="Link to external resource: http://creativecommons.org/licenses/by-nc-nd/4.0/">Creative Commons Attribution-NonCommercial-NoDerivs</a> License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.