The Seven Crystal Balls (1943-1946, 1948 ) 14. Prisoners of the Sun (1946-1948, 1949 ) 15. Land of Black Gold (1948-1950, 1950 , 1971) 16. Destination Moon (1950-1953, 1953 ) 17. Explorers on the Moon (1950-1953, 1954 ) 18. The Calculus Affair (1954-1956, 1956 ) 19. The Red Sea Sharks (1956-1958, 1958