Central banking and monetary policy – which will be the new normal? is a one day conference co-organized by SUERF/BAFFI Carefin. Right on time BIS has published research discussing negativity of negative interest rates.

https://www.bis.org/publ/qtrpdf/r_qt1603e.htm

Financial Times discusses the matter with invited guests in their video blogg

http://www.ft.com/intl/cms/s/0/206f3528-e393-11e5-a09b-1f8b0d268c39.html#axzz42AZOBSUO