János Bolyai Mathematical Society and Springer-Verlag Berlin Heidelberg Posted on October 20, 2014 by SCG DR Copyright Holders: János Bolyai Mathematical Society and Springer-Verlag Berlin Heidelberg a Self-archiving policy Conditions Accepted version: √ 12 months embargo Published version: X a Remarks: Follow Springer’s self-archiving policy. (verified by Bo Siang via email) Verification Date: 16.10.2014