RT Journal Article SR Electronic T1 Interferon β-1a prevented the development of clinically definite multiple sclerosis after a first demyelinating event JF Evidence Based Medicine JO Evid Based Med FD BMJ Publishing Group Ltd SP 78 OP 78 DO 10.1136/ebm.6.3.78 VO 6 IS 3 YR 2001 UL http://ebm.bmj.com/content/6/3/78.abstract AB