SIMBAD references

High-precision UBV(RI)_c photometry of 23 selected acitve stars, collected at the European Southern Observatory (La Silla, Chile) over the period 9-28 December 1989, is presented. This paper is part of a larger program focusing on the global properties and evolution of active stars and is aimed at establishing a time-extended database which can give important clues on topics such as the stability of the spotted areas, differential rotation and solar-like cycles. Significant evolution of the wave-like light curves, period variations and, in most cases, evidence for long-term variability of the global degree of spottedness are found for the observed stars. Some spectral classifications are rediscussed and evidence for a newly discovered variable star is given.