© 2015 Author(s). This is an Open Access article 
distributed under the terms of the Creative Commons CC-BY-NC 4.0 License 
(http://creativecommons.org/licenses/by-nc/4.0/), allowing third parties to copy and 
redistribute the material in any medium or format and to remix, transform, and build upon the 
material for non-commercial use, provided th
e original author and source are credited
Med mindre annet er angitt, så er denne innførselen lisensiert som © 2015 Author(s). This is an Open Access article distributed under the terms of the Creative Commons CC-BY-NC 4.0 License (http://creativecommons.org/licenses/by-nc/4.0/), allowing third parties to copy and redistribute the material in any medium or format and to remix, transform, and build upon the material for non-commercial use, provided th e original author and source are credited