The evaluation of enhanced feedback interventions to reduce unnecessary blood transfusions (AFFINITIE): protocol for two linked cluster randomised factorial controlled trials oleh Suzanne Hartley, Robbie Foy, Rebecca E. A. Walwyn, Robert Cicero, Amanda J. Farrin, Jill J. Francis, Fabiana Lorencatto, Natalie J. Gould, John Grant-Casey, Jeremy M. Grimshaw, Liz Glidewell, Susan Michie, Stephen Morris, Simon J. Stanworth, for the AFFINITIE programme