ball crossing third base

[shipwreck]

In a previous post, it was talked about a ball bounding over third base. Here is my question. A hit ball that last touches in foul ground and then crosses over third base or touches third base is a fair or foul ball? Please site rule reference. I have brought this up to numerous umpires and they all say fair ball, but umpires on this site say foul. I always thought it would be a fair ball. Dave