To save this article to your Kindle, first ensure [email protected] is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.

Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.

Find out more about the Kindle Personal Document Service.

Reply to: Submit a response

Title * Please enter a title for your response.

Contents * Please enter your response.

Your details

First name * Please enter your first name.

Last name * Please enter your last name.

Please enter a valid email address.

Occupation Please enter your occupation.

Affiliation Please enter any affiliation.

You have entered the maximum number of contributors

Conflicting interests

Do you have any conflicting interests? * Conflicting interests help

Yes No

More information * Please enter details of the conflict of interest or select 'No'.

Please tick the box to confirm you agree to our Terms of use. *

Please accept terms of use.

Please tick the box to confirm you agree that your name, comment and conflicts of interest (if accepted) will be visible on the website and your comment may be printed in the journal at the Editor’s discretion. *

Please confirm you agree that your details will be displayed.

Article contents

ADVERTISEMENTS

Abstract

Access options

This article has been cited by the following publications. This list is generated based on data provided by Crossref.