Yin, Jun http://orcid.org/0000-0003-2706-0620
Porporato, Amilcare http://orcid.org/0000-0001-9378-207X
Article History
Received: 26 May 2017
Accepted: 23 November 2017
First Online: 22 December 2017
Competing interests
: The authors declare no competing financial interests.