@book { DasSchriftformerfordernisnach550BGB, title = "Das Schriftformerfordernis nach ยง 550 BGB", author = "Isabel {Reingardt}", year = "2013", publisher = "Peter Lang Verlag", address = "Berlin, Germany", doi = "10.3726/978-3-653-02344-2", url = "https://www.peterlang.com/document/1046178" }