No neurochemical evidence for brain injury caused by heading in soccer
Henrik Zetterberg, Michael Jonsson, Abdullah Rasulzada, Cornel Popa, Ewa Styrud, Max Albert Hietala, Lars Rosengren, Anders Wallin, Kaj Blennow
British Journal of Sports Medicine Sep 2007, 41 (9) 574-577; DOI: 10.1136/bjsm.2007.037143