© 2016 The author(s). 
This is an Open Access article distributed under the terms 
of the 
Creative Commons Attribution 4.0 International
License, which permits 
unrestricted use, 
distribution, and reproduction in any medium, provided the original work is properly credited.
Med mindre annet er angitt, så er denne innførselen lisensiert som © 2016 The author(s). This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 International License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.