@book { Verkaufsmanagementdie13StufendesVerkaufs, title = "Verkaufsmanagement - die 13. Stufen des Verkaufs", author = "Moritz {Wenninger}", year = "2013", publisher = "GRIN Verlag", address = "München, Germany", doi = "10.3239/9783656365570", url = "https://www.hausarbeiten.de/document/208653" }