Robson SC, Kelly T, Howel D, Deverill M, Hewison J, Lie ML, Stamp E, Armstrong N, May CR. Randomised preference trial of medical versus surgical termination of pregnancy less than 14 weeks' gestation (TOPS). Health Technol Assess. 2009 Nov;13(53):1–124, iii. doi: 10.3310/hta13530. PMID: 19906334.