Die drei Fragezeichen (Original) is a 33-book series with 33 primary works first released in 1964 with contributions by Robert Arthur, William Arden, and 3 others.
1964 • 8 Readers • 192 pages • 3.2
1965 • 2 Readers • 185 pages • 3.5
1967 • 2 Readers • 164 pages • 3
1968 • 2 Readers • 184 pages • 3
1964 • 2 Readers • 182 pages • 3
1966 • 2 Readers • 160 pages • 3
1971 • 1 Reader • 3
1978 • 1 Reader • 144 pages • 4
1978 • 1 Reader • 152 pages • 4