21.   When it comes to knocking heads, nobody in the league has been as efficient as the Chiefs.

22.   When your head is knocked against the turf, there is no cushion.

23.   Would you want to knock heads with him?

24.   Bjork continued to assault Kaufman as the journalist fell to the floor, grabbing her hair and knocking her head against the ground.

25.   But during negotiations between bitter rivals, Zinni is less inclined to knock heads as he is to craft thoughtful, realistic compromises, those who know him say.

26.   He fell to his knees and knocked his head to the ground in frustration.

27.   He fell to his knees and knocked his head against the ground in frustration.

28.   Ivanisevic and Philippoussis knocked heads when both tried to head a dead ball soccer style.

29.   Knocking his head with his right hand three times, it seemed like he had once again failed under pressure.

30.   Teammate Klaus Kroell was also injured, falling at the same place and knocking his head.