M. Becker, M. Böttcher, and S. Klingner. RESER 2011 Productivity of Services NextGen - Beyond Output / Input. Conference Proceedings, (8th/9th September 2011)
M. Becker, M. Böttcher, and S. Klingner. RESER 2011 Productivity of Services NextGen - Beyond Output / Input. Programme and Abstracts, page 183--184. (8th/9th September 2011)