Text and Data Mining valid from 2016-09-20
Received: 21 June 2015
Accepted: 3 August 2016
First Online: 20 September 2016
: T. Kunieda and T.H. declare competing financial interests, as a part of the work described in this publication has been applied for a patent (Japanese patent application number 2015-032209). All other authors declare no competing financial interests.