Duarte, Luís http://orcid.org/0000-0001-9391-3041
Khriachtchev, Leonid http://orcid.org/0000-0002-1146-5212
Article History
Received: 17 March 2017
Accepted: 19 April 2017
First Online: 9 June 2017
Competing Interests
: The authors declare that they have no competing interests.