Funding for this research was provided by:
Ministerio de Economía y Competitividad (MAT2015-68078-R)
National Science Foundation (1139792)
Article History
Received: 22 June 2016
Accepted: 12 July 2016
First Online: 22 July 2016
Compliance with ethical standards
:
: The authors state that there is no conflict of interest that could potentially influence or bias the submitted work.