Part of this work is supported by the Russian "Astronomy" program project N1.3.2. I thank Booth Hartley (IPAC Caltech) for a good package, "Skyview" ver.3.3 for Linux, Dr. E. Fürst (Max-Planck-Institut für Radioastronomie) for FITS maps of the Galactic plane surveys and NRAO for FITS maps of the NVSS survey. I am very grateful to an anonymous referee for helpful suggestions.
© European Southern Observatory (ESO) 1999
Online publication: December 2, 1999