Trial feasibility and process evaluation of a motivationally-embellished group peer led walking intervention in retirement villages using the RE-AIM framework: The Residents in Action Trial (RiAT) - Thogersen-Ntoumani, Cecilie; Quested, Eleanor; Biddle, S.; Kritz, Marlene; Olson, Jenny; Burton, Elissa; Cerin, E.; Hill, Keith D.; McVeigh, Joanne; Ntoumanis, Nikos (Taylor & Francis, 2019)