The mystery of the vanishing treasure / by Robert Arthur originally published: New York : Random House, 1966 ; London : Collins, 1968 - The secret of Phantom Lake / by William Arden originally published: New York : Random House, 1973 ; London : Collins, 1974 - The mystery of the dancing devil / by William Arden originally published: New York : Random House, 1976 ; London : Collins, 1977.
