@book{Laack2022,
  author    = {Laack, Walter van},
  title     = {Aufruf zum Nachdenken: Corona und neue Kriege - Wie kann die Menschheit {\"u}berleben?},
  publisher = {van Laack GmbH},
  address   = {Aachen},
  isbn      = {978-3-936624-56-4},
  pages     = {56 Seiten},
  year      = {2022},
  language  = {de}
}
@book{Grueters1987,
  author    = {Gr{\"u}ters, Hugo},
  title     = {Aufgabensammlung Mechanik / von Hugo Gr{\"u}ters},
  publisher = {Becker-Kuns},
  address   = {Aachen},
  pages     = {Getr. Z{\"a}hlung : graph. Darst.},
  year      = {1987},
  language  = {de}
}