Licence information
This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice.No use, distribution or reproduction is permitted which does not comply with these terms.
Copyright statements
Copyright © 2014 Williams and McOwan. This document is protected by copyright and was first published by Frontiers. All rights reserved. It is reproduced with permission.
