Rumble, John R. Jr
Article History
Received: 16 February 2017
Accepted: 7 May 2017
First Online: 5 June 2017
Compliance with Ethical Standards
:
: The mention of specific privately owned and operated data resources implies neither endorsement nor criticism. These data resources are mentioned as examples or for illustrative purposes.
: Not applicable.
: The author declares that there is no competing interest.