Association between recruitment methods and attrition in Internet-based studies.

Bajardi P;Paolotti D;Vespignani A;Eames K;Funk S;Edmunds WJ;Turbelin C;Debin M;Colizza V;Smallenburg R;Koppeschaar C;Franco AO;Faustino V;Carnahan A;Rehn M;Merletti F;Douwes J;Firestone R;Richiardi L