Hardy-guttene is a 37-book series with 37 primary works first released in 1920 with contributions by Franklin W. Dixon, Jerrold Mundis, and Leslie H. Morrill.
1927 • 36 Readers • 214 pages • 3.4
1927 • 19 Readers • 138 pages • 3.5
1982 • 1 Reader • 181 pages • 3