Notes. 1: Some of them may be eruptive binaries. 2: Variability photographically not established (too faint, blends or too small amplitudes). 3: Chromospherically active stars (RS CVn and BY Dra). 4: Slow irregular and semiregular variables of late spectral type (see GCVS, Kholopov 1985), some of which may possibly also be related to the chromospherically active stars. 5: Mostly overexposed on the photographic plates, and thus not investigated for variability. Because of the scarcity of bright stars as counterparts of ROSAT sources, these matches are likely real associations (see Fig. 40). These stars are therefore with high probability chromospherically active stars. 6: Flare stars of UV Cet type. 7: Mainly cataclysmic variables (CVs), but also X-ray binaries of AM Her type. 8: 7 X-ray sources close together, since source detection algorithm was optimized for point sources. 9: Out of the 25 unclassified objects in the Com field (dash in the last column of Table 1), the error circle of 9 objects is empty on the DSS2 (about B ~ 20th mag), and for another 17 X-ray sources (totalling 26), no optical object is visible on the Sonneberg astrograph plates (about B ~ 17th mag). 10: Positional coincidence implies secure correlation, but source type remains open.