@book { PredictingItemDifficultyinaReadingTest,
    title = "Predicting Item Difficulty in a Reading Test",
    author = "Klaus {Siller}",
    year = "2020",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    doi = "10.3726/b16819",
    url = "https://www.peterlang.com/document/1059038"
}