Die drei Fragezeichen (Original) is a 40-book series with 40 primary works first released in 1964 with contributions by Robert Arthur, William Arden, and 4 others.
1964 • 10 Readers • 159 pages • 3.3
1965 • 2 Readers • 185 pages • 3.5
1967 • 2 Readers • 164 pages • 3
1968 • 2 Readers • 184 pages • 3
1970 • 1 Reader • 157 pages • 4
1964 • 1 Reader • 169 pages • 4
1974 • 1 Reader • 139 pages • 4
1971 • 1 Reader • 3
1978 • 1 Reader • 144 pages • 4
1978 • 1 Reader • 152 pages • 4