Comment on “Zircon U-Th-Pb dating using LA-ICP-MS: simultaneous U-Pb and U-Th dating on 0.1 Ma Toya Tephra, Japan” by Hisatoshi Ito - Guillong, Marcel; Schmitt, Axel Karl; Bachmann, Olivier (Journal of volcanology and geothermal research, 2015)