@book { ContractLawinElectronicCommerce,
    title = "Contract Law in Electronic Commerce",
    author = "Ralf {Holthöfer}",
    year = "2001",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832430610",
    url = "https://m.diplom.de/document/218774"
}