Simultaneous variations in Markarian 421 in the optical and TeV-range - Pfeiffer, Marion; Wagner, Stefan; Dietrich, Matthias (Abstracts of contributed talks and posters presented at the Joint Scientific Fall Meeting of the Astronomische Gesellschaft and of the Arbeitsgemeinschaft Extraterrestrische Forschung (AEF/DPG) at Bonn, 1995)