1. Ackermann, G., Fugmann, G., Hermann, W., and Voeleker, K.: 1968,Z. Astrophys. 69, 130.
2. Alter, G., Ruprecht, J., and Van�sek, V.: 1958,Catalogue of Star Clusters and Associations, Publ. House Czech Acad. Sci., Prague.
3. Baars, J. W. M. and Wendker, H. J.: 1974, in S. C. Simonson and F. J. Kerr (eds.), ?Galactic Radio Astronomy?,IAU Symp. 60.
4. Balick, B.: 1972,Astrophys. J. 176, 353.
5. Becker, W. and Fenkart, R.: 1963,Z. Astrophys. 56, 257.