Allan, Roy A. (2001): . Allan Publishing. ISBN 0-9689108-0-7. Blaxill, Mark; Eckardt, Ralph (5. mars 2009): The Invisible Edge: Taking Your Strategy to the Next Level Using Intellectual Property. Portfolio Hardcover. ISBN 1591842379. Pietrek, Matt (Mars 1996): , (PDF). IDG. ISBN 1-56884-318-6.