NUMA 6 - Polar Shift
Cussler, Clive
Undersea City
Frederik Pohl & Jack Williamson
Undersea (1)
Bolos III: The Triumphant
Keith Laumer & Bill Fawcett
NUMA 1 - Serpent
The Sea of Adventure
Enid Blyton
Adventure (4)
Tanar of Pellucidar
Edgar Rice Burroughs
Pellucidar (3)
The Secret Island
Secret (1)