What is the best time point to identify patients at risk of developing persistent low back pain? - Melloh, Markus; Elfering, Achim; Käser, Anja; Rolli Salathé, Cornelia; Crawford, Rebecca J.; Barz, Thomas; Zweig, Thomas; Aghayev, Emin; Röder, Christoph; Theis, Jean-Claude (Journal of Back & Musculoskeletal Rehabilitation, 2015)