There are 2 sets of rules with this name.
Crossfire Variant[]
Vietnam conversion for Crossfire by Barrie Lovell the author of Free Fire Zone.
http://balagan.info/incoming-vietnam-rules-for-the-crossfire-system-by-barrie-lovell
http://web.archive.org/web/20110504052148/http://www.eleven-bravo.co.uk/wargaming/incoming/index.php
One page Rules[]
A set of one-page, fast-play rules for WWII, post-war and modern combat at the operational level.