@book { DieRegulierungvonnatrlichenMonopolen,
    title = "Die Regulierung von natürlichen Monopolen",
    author = "Thomas {Rieger}",
    year = "1999",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832417604",
    url = "https://m.diplom.de/document/217624"
}