@book{WickelHartogh2004,
  author    = {Wickel, Hans Hermann and Hartogh, Theo},
  title     = {Handbuch Musik in der Sozialen Arbeit},
  publisher = {Juventa},
  address   = {Weinheim},
  isbn      = {3-7799-0787-9},
  pages     = {496 S.: graph. Darst.},
  year      = {2004},
  language  = {de}
}
@book{WickelHartogh2006,
  author    = {Wickel, Hans Hermann and Hartogh, Theo},
  title     = {Musik und H{\"o}rsch{\"a}den},
  edition   = {1. Aufl.},
  publisher = {Juventa-Verl.},
  address   = {Weinheim [u.a.]},
  isbn      = {3-7799-1951-6},
  pages     = {184 S. : Ill., graph. Darst.},
  year      = {2006},
  language  = {de}
}
@book{WickelHartogh2008,
  author    = {Wickel, Hans Hermann and Hartogh, Theo},
  title     = {Musizieren im Alter},
  edition   = {1. Aufl.},
  publisher = {Schott},
  address   = {Mainz [u.a.]},
  isbn      = {978-3-7957-87},
  pages     = {163 S. : Ill., graph. Darst.},
  year      = {2008},
  language  = {de}
}
@book{WickelHartogh2011,
  author    = {Wickel, Hans Hermann and Hartogh, Theo},
  title     = {Praxishandbuch Musizieren im Alter},
  edition   = {1. Aufl.},
  publisher = {Schott Music},
  address   = {Mainz},
  isbn      = {978-3-7957-8747-9},
  year      = {2011},
  language  = {de}
}