Mysteries of History: Mystery of the Sphinx
The Central Intelligence Agency: An Encyclopedia of Covert Ops, Intelligence Gathering, and Spies
Investigating Witches and Witchcraft
9/11 and the War on Terror: A Documentary and Reference Guide
Secret Societies and Clubs in American History
Investigating Atlantis and Other Lost Cities
Investigating the Abominable Snowman and Other Legendary Beasts
Investigating Ghosts and the Spirit World
Disasters and Tragic Events: An Encyclopedia of Catastrophes in American History