21. The Great airport mystery Title: The Great airport mystery Date: 1930[1964] Author: Dixon Collecting Area: Mathes Childrens Literature
22. The Tower treasure Title: The Tower treasure Date: 1959 [1965] Author: Dixon Collecting Area: Mathes Childrens Literature
23. The Mystery of cabin island Title: The Mystery of cabin island Date: 1966 [1976] Author: Dixon Collecting Area: Mathes Childrens Literature
24. The Clue of the broken blade Title: The Clue of the broken blade Date: 1942 [1958] Author: Dixon Illustrator: Illus. by Paul Laune Collecting Area: Mathes Childrens Literature