G. Schuh, C. Hoffart, G. Gudergan, and J. Siegers. Management industrieller Dienstleistungen: Handbuch Produktion und Management 8, chapter 6, Springer Vieweg, Berlin, 2 edition, (2016)
M. Müller. Privacy and Identity Management for Emerging Services and Technologies, volume 421 of IFIP Advances in Information and Communication Technology, Springer, Heidelberg, (2015)