Funding for this research was provided by:
Israel Science Foundation (399/16)
United States - Israel Binational Science Foundation (2014337)
Division of Mathematical Sciences (1464479)
Van Vleck Professorship Research Award
Russian Science Foundation (14-21-00025)
Article History
Received: 15 May 2018
Accepted: 27 September 2018
First Online: 23 October 2018