Multiwavelength optical observations of chromospherically active binary systems - V. FF UMa (2RE J0933+624): a system with orbital period variationM. C. Gálvez, D. Montes, M. J. Fernández-Figueroa, E. De Castro and M. CornideA&A, 472 2 (2007) 587-598DOI: https://doi.org/10.1051/0004-6361:20067015