@article{GrassmannMirwaldKlunteretal.2000,
  author    = {Grassmann, Marianne and Mirwald, Elke and Klunter, Martina and Veith, Ute},
  title     = {Untersuchungen {\"u}ber Vorkenntnisse von Schulkindern zu zentralen Inhalten des Mathematikunterrichts der Klasse 4, Teil 2},
  year      = {2000},
  language  = {de}
}
@article{GrassmannMirwaldKlunteretal.2000,
  author    = {Grassmann, Marianne and Mirwald, Elke and Klunter, Martina and Veith, Ute},
  title     = {Untersuchungen {\"u}ber Vorkenntnisse von Schulkindern zu zentralen Inhalten des Mathematikunterrichts der Klasse 4, Teil 1},
  year      = {2000},
  language  = {de}
}