A systematic review of evidence to inform HIV prevention interventions among men who have sex with men in Europe Strömdahl, S and Hickson, F and Pharris, A and Sabido, M and Baral, S and Thorson, A, Eurosurveillance, 20, 21096 (2015), https://doi.org/10.2807/1560-7917.ES2015.20.15.21096