Correction: Descriptive, cross-country analysis of the nurse practitioner workforce in six countries: size, growth, physician substitution potential

Maier CB, Barnes H, Aiken LH, et al. Descriptive, cross-country analysis of the nurse practitioner workforce in six countries: size, growth, physician substitution potential. BMJ Open 2016;6:e011901. Complete publication details of references 36, 39–41, 53, 77, 81 and 82 are given below. 36. Maier CB, Aiken LH. Task-shifting from physicians to nurses in primary