Die drei Fragezeichen is a 99-book series with 96 released primary works first released in 1993 with contributions by Brigitte Johanna Henkel-Waidhofer, André Marx, Ben Nevis, André Minninger, Katharina Fischer, Robert Arthur, Alfred Hitchcock, Marco Sonnleitner, Ingeborg Urspruch, Astrid Vollenbruch, Kari Erlhoff, Hendrik Buchna, Christoph Dittert, and C.R. Rodenwald.