RT Journal Article SR Electronic T1 Calendar JF British Journal of Sports Medicine JO Br J Sports Med FD BMJ Publishing Group Ltd and British Association of Sport and Exercise Medicine SP 259 OP 260 DO 10.1136/bjsm.23.4.259 VO 23 IS 4 YR 1989 UL http://bjsm.bmj.com/content/23/4/259.abstract AB