What is the formula for battle outcome calculation?

Does anyone know what is the formula?
For example if a 13 strength unit attacks an 11 strength unit, how much damage does it inflict? (no modifiers, no bonuses, no over river attack - just normal attack)

I've been searching around for this too, but it just seems to be too complex

http://forums.civfanatics.com/showthread.php?t=432238

This was the best I could find, but that's only relevant for Vanilla, not G&K.