Version 3.5 is a refinement of Version3, which of course was based apon Version 2 and 1 before it.
As Version 3 is depreciated, I wont be hosting or referancing it on my site beyound this mention. Version3 can be tracked down in second hand shops, but I urge not to bother.
3.5 is almost certainly one of the most played rulesets, certainly the most official matchs have taken place under it. If you wish to play a profesional game, this is absolutely a must have.