Efficacy and safety of 6.25 mg t.i.d. feverfew CO2-extract (MIG-99) in migraine prevention--a randomized, doubleblind, multicentre, placebo-controlled study - Diener, HC; Pfaffenrath, V; Schnitker, J; Friede, M; Henneicke-von Zepelin, HH (Cephalalgia, 2005)