Mr. Hagmann is the author of Tactical Surveillance, An Investigator's Guide to Conducting Surveillance Operations. 
He is a frequent guest on several AM talk radio venues such as Coast to Coast AM and on Steve Quayle's "Q-files" shortwave and internet broadcasts. He frequently appears as a talk show guest with Steve Quayle in tow.
One of his coauthors is Maria Kneas.
Northeast Intelligence Network
A Subsidiary of Tactical Publications
P.O. Box 9534
Erie, PA 16505-8534
Email for Hagmann: director AT homelandsecurityus.com