title: Aggressive and non-aggressive fighting in twelve-to-thirteen year old pre-adolescent boys.
mesh_terms: D000293:Adolescent; D000367:Age Factors; D000374:Aggression; D002648:Child; D002653:Child Behavior Disorders; D002657:Child Development; D005149:Facial Expression; D006791:Hostility; D006801:Humans; D008297:Male; D010988:Play and Playthings; D011627:Puberty; D012919:Social Behavior