The "thriller-like Mind Brothers sf series, which combines a great deal of fairly convoluted action with Time Travel"
(underscore represents linked cross-reference)
--SFE3, biographical entry by John Clute and David Langford
Front cover capsules (Lancer and Magnum eds.):
1. The last man alive in Earth's dim future helps foil a deadly espionage plot ... today!
2. That dark day in Dallas ... The President's shocking death ... led the Mind Brothers on a quest across centuries for fantastic villains.
3. You don't want the world to end? Then don't push that button ...