Using Intervention Mapping to Develop a Decision Support System–Based Smartphone App (selfBACK) to Support Self-management of Nonspecific Low Back Pain: Development and Usability Study - Malene Jagd Svendsen; Louise Fleng Sandal; Per Kjær; Barbara I Nicholl; Kay Cooper; Frances Mair; Jan Hartvigsen; Mette Jensen Stochkendahl; Karen Søgaard; Paul Jarle Mork; Charlotte Rasmussen (Journal of Medical Internet Research, 2022)