@book{GuderHerrmannLuethjeetal.2007,
  author    = {Klaus-Ulrich Guder and Caroline Herrmann and Thomas L{\"u}thje and Silke Pyroth},
  title     = {Beobachtungshefte (10 Ex.) : 1.-4. Schuljahr},
  isbn      = {978-3-12-300001-0},
  year      = {2007},
}