Funding for this research was provided by:
Directorate for Mathematical and Physical Sciences (DMS-1361421)
Directorate for Mathematical and Physical Sciences (DMS-1318480, DMS-1217153)
European Social Fund (CZ.1.07/2.3.00/30.0034)
Article History
Received: 8 August 2014
Accepted: 27 August 2016
First Online: 12 September 2016