Observer bias in randomized clinical trials with time-to-event outcomes: systematic review of trials with both blinded and non-blinded outcome assessors.
Hróbjartsson A, Thomsen A S S, Emanuelsson F, Tendal B, Rasmussen J V, Hilden J, Boutron I, Ravaud P, Brorson S
Int J Epidemiol. 2014 Jan 21. PMID: 24448109.Abstract