Efficacy and safety of an ethanolic solution of peppermint oil for patients with episodic tension type headache: EUMINZ® a randomized controlled trial - Shah, Y; Spoo, M; Jeitler, M; Steckhan, N; Stange, R; Uehleke, B; Michalsen, A (Zeitschrift für Phytotherapie, 2017)