@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 = "2024-05-16"
}