@book { DieeinseitigverpflichtendeSchuldzusage,
    title = "Die einseitig verpflichtende Schuldzusage",
    author = "Niklas {Wielandt}",
    year = "2021",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1135484"
}