The Mystery of the Sinister Scarecrow (1979) - Front cover of ''The Mystery of the Sinister Scarecrow''.The Mystery of the Dead Man's Riddle (1974) - Front cover of ''The Mystery of the Dead Man's Riddle''The Mystery of the Moaning Cave (1968) - Front cover of ''The Mystery of the Moaning Cave''.The Mystery of the Shrinking House (1972) - Front cover of ''The Mystery of the Shrinking House''.The Mystery of the Whispering Mummy (1965) - Front cover of ''The Mystery of the Whispering Mummy''.The Mystery of the Laughing Shadow (1969) - Front cover of ''The Mystery of the Laughing Shadow''.The Mystery of the Coughing Dragon (1970) - Front cover of ''The Mystery of the Coughing Dragon''.The Mystery of the Death Trap Mine (1976) - Front cover of ''The Mystery of the Death Trap Mine''.The Three Investigators - Front cover from the ''The Three Investigators'' series.The Mystery of the Coughing Dragon (1970) - Front cover of ''The Mystery of the Coughing Dragon''.The Mystery of the Talking Skull (1969) - Front cover of ''The Mystery of the Talking Skull''.The Mystery of the Coughing Dragon (1970) - Illustration for the Danish release of ''The Mystery of the Coughing Dragon'' by artist Peter Madsen.The Mystery of the Vanishing Treasure (1966) - Front cover of ''The Mystery of the Vanishing Treasure''.The Mystery of the Monster Mountain (1973) - Front cover of ''The Mystery of the Monster Mountain''.The Secret of the Haunted Mirror (1974) - Front cover of ''The Secret of the Haunted Mirror''.