@book { InternetbasedTechnologiesandSystemsforthesupportofindirectprocurement,
    title = "Internet based Technologies and Systems for the support of indirect procurement",
    author = "Christian {Epp}",
    year = "2001",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832440107",
    url = "https://m.diplom.de/document/219645"
}