I K Crombie, W C S Smith, P D Campion, J D E Knox
Crombie I K, Smith W C S, Campion P D, Knox J D E.
Comparison of response rates to a postal questionnaire from a general practice and a research unit
Br Med J (Clin Res Ed) 1986; 292 :140
doi:10.1136/bmj.292.6513.140-d