Conrad, Frederick G; Erens, B; Burkill, S; Clifton, S; Tanton, C; Phelps, A; Datta, J; Mercer, C H; Sonnenberg, P; Prah, P; Mitchell, K R; Wellings, K; Johnson, A M; Copas, A J. (2014).
Nonprobability Web surveys to measure sexual behaviors and attitudes in the general population: a comparison with a probability sample interview survey. Journal of medical Internet research. 16, e276.