Doward L, Svedsater H, Whalley D, Crawford R, Leather D, Lay-Flurrie J, Bosanquet N. Salford Lung Study in chronic obstructive pulmonary disease (SLS COPD): follow-up interviews on patient-centred outcomes. NPJ Prim Care Respir Med. 2017 Dec 15;27(1):66. doi: 10.1038/s41533-017-0066-2
Hahn EJ, Rayens MK, Warnick TA, Chirila C, Rasnake RT, Paul TP, Christie D. A controlled trial of a quit and win contest. Am J Health Promot. 2005 Nov 1;20(2):117-26.