Evaluating a complex system-wide intervention using the difference in differences method: the Delivering Choice Programme
Jeff Round, Robyn Drake, Edward Kendall, Rachael Addicott, Nicky Agelopoulos, Louise Jones
BMJ Supportive & Palliative Care Mar 2015, 5 (1) 26-33; DOI: 10.1136/bmjspcare-2012-000285