Planck 2016 intermediate results. XLVII. Planck constraints on reionization history

Acknowledgements. The Planck Collaboration acknowledges the support of: ; CNES, and CNRS/INSU-IN2P3-INP (France); ASI, CNR, and INAF (Italy); NASA and DoE (USA); STFC and UKSA (UK); CSIC, MINECO, J.A., RES (Spain); Tekes, AoF, and CSC (Finland); DLR and MPG (Germany); (Canada); DTU Space (Denmark); SER/SSO (Switzerland); RCN (Norway); SFI (Ireland); FCT/MCTES (Portugal); ERC and PRACE (EU). A description of the Planck Collaboration and a list of its members, indicating which or scientific activities they have been involved in, can be found at ://www.cosmos.esa.int/web/planck/planck-collaboration