@book { ControllinginmittlerenUnternehmensberatungen, title = "Controlling in mittleren Unternehmensberatungen", author = "Stefan {Seibert}", year = "2011", publisher = "Diplom.de", address = "Hamburg, Germany", doi = "10.3239/9783842814639", url = "https://m.diplom.de/document/228501" }