Based on observations collected at the European Southern Observatory, Chile.

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Table 4 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html
Correspondence to: massi@coma.mporzio.astro.it

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...(DSS

The Digitized Sky Survey was produced at the Space Telescope Science Institute under U. S. Government grant NAG W-2166. The images of these surveys are based on photographic data obtained using the Oschin Schmidt Telescope on Palomar Mountain and the UK Schmidt Telescope.

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