1. MRC Clinical Trials Unit; Meta-analysis Group; 125 Kingsway London UK WC2B 6NH
2. MRC Clinical Trials Unit at UCL; Meta-analysis Group; Aviation House 125 Kingsway London UK WC2B 6NH
3. MRC Clinical Trials Unit; 125 Kingsway London UK WC2B 6NH
4. Medical Research Council; Social and Public Health Sciences Unit; 4 Lilybank Gardens Glasgow UK G12 8RZ
5. University College London; Research Department of Primary Care and Population Health; Royal Free Campus Rowland Hill Street London UK NW3 2PF