I posted this is on the other thread and its valuable here:
Rule 8, Section 1, Article 3, Item 1 states:
Player Going to the Ground. If a player goes to the ground in the act of catching a pass (with or without contact by an opponent), he must maintain control of the ball throughout the process of contacting the ground, whether in the field of play or the end zone. If he loses control of the ball, and the ball touches the ground before he regains control, the pass is incomplete. If he regains control prior to the ball touching the ground, the pass is complete.