Longterm optical monitoring of bright BL Lacertae objects with ATOM: Spectral variability and multiwavelength correlationsAlicja Wierzcholska, Michał Ostrowski, Łukasz Stawarz, Stefan Wagner and Marcus HauserA&A, 573 (2015) A69DOI: https://doi.org/10.1051/0004-6361/201423967
