@online{ timsrc, author = "Marggraf, Rainer", title = "Herausforderung Umwelt", publisher = "Universität Tübingen", year = "2001", month = "Dec", day = "18", url = "https://timms.uni-tuebingen.de:443/tp/UT_20011218_001_umwelt_0001", urldate = "2024-11-27" }