@book { ChancenundGrenzendesProblemBasedLearning,
    title = "Chancen und Grenzen des Problem-Based Learning",
    author = "Helmut {Wallner}",
    year = "2008",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783836609593",
    url = "https://m.diplom.de/document/225582"
}