References

• Bade N., Engels D., Voges W., et al., 1998, A&AS 127, 145 NASA ADS
• Brinkmann W., Siebert J., Reich W., et al., 1995, A&AS 109, 147 NASA ADS
• Cao L., Wei J.Y., Hu J.Y., 1998 (to be submitted A&A)
• Maccacaro T., Gioia I., Wolter A., et al., 1988, ApJ 326, 680 NASA ADS
• Monet D.G., et al., 1996, USNO-A1.0. Washington DC, USNO
• Stocke J.T., Morris S.L., Gioia I.M., et al., 1991, ApJS 76, 813 NASA ADS
• Strom K.M., 1979, Kitt Peak National Observatory IIDS Standard Star Manual
• Véron-Cetty M.-P., Véron P., 1996, ESO Scientific Report, No.17
• Voges W., 1992, in Proceedings of the ISY Conference "Space Sciences", ESA ISY-3, ESA Publications, p.9
• Voges W., Gruber R., Haberl F., et al., 1994, ROSAT NEWS No. 392
• Voges W., Boller Th., Dennerl K., et al., 1996a, MPE-Report 263, 637
• Voges W., Aschenbach B., Boller Th., et al., 1996b, IAU Circ. 6420
• Voges W., Aschenbach B., Boller Th., et al., 1997 (to be submitted A&AS)
• Wei J.Y., Cao L., Hu J.Y., et al., 1996, in Proceedings of IAU Colloquium 159, p.425
• Wei J.Y., Cao L., Xu D.W., et al., 1997, Acta Astrophys. Sin. 17, 107
• Yan H.J., 1995 (private communication)