1. Ekkernkamp M, Mittag O, Matthis C, Raspe A, et al. (2004). [Physical impairments and comorbidities in a sample of members of a pension fund of blue-collar workers suffering from severe low back pain]. Zeitschrift fur Orthopadie und Ihre Grenzgebiete 142(6):720-6.
2. Raspe A, Matthis C, Heon Klin V, Raspe H. (2003). [Chronic back pain: More than pain in the back. Findings of a regional survey among insurees of a workers pension insurance fund]. Rehabilitation 42(4):195-203.
3. Raspe A, Matthis C, Heon-Klin V, Raspe H. (2003). [Chronic back pain: more than pain in the back. Findings of a regional survey among insurees of a workers pension insurance fund]. Rehabilitation 42(4):195-203.