When checking your documents at check-in (if in doubt) airlines are using IATA publication called "Timatic" - http://en.wikipedia.org/wiki/Timatic (exists in many forms incl printed and comp database).

Here you can use it free of charge http://www.iatatravelcentre.com/ but you will get only a "user friendly" output which should be enough in most cases. Some airline websites (like Virgin and Delta quoted above) also providing extract from Timatic.