@online{ timsrc, author = "Grammig, Joachim", title = "Lecture Applied Econometrics, 21. Lesson", publisher = "Universität Tübingen", year = "2020", month = "May", day = "25", url = "https://timms.uni-tuebingen.de:443/tp/UT_20200525_001_appecono_0001", urldate = "2024-11-23" }