Based on observations made at Complejo Astronómico El Leoncito, which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina (CONICET) and the National Universities of La Plata, Córdoba and San Juan, Argentina.

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Tables 2-4 and Appendix are only available in electronic form at http://www.aanda.org

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... IRAF

IRAF is distributed by the National Optical Astronomy Observatories, which is operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.

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