@book { WhyBanks,
    title = "Why Banks?",
    subtitle = "Microeconomic Foundations of Financial Intermediaries",
    author = "Ilonka {Rühle}",
    year = "1998",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    doi = "10.3726/978-3-653-02210-0",
    url = "https://www.peterlang.com/document/1051866"
}