Simon Newcomb, Tables of the Four Inner Planets, vol. 6 dels Astronomical Papers Prepared for the Use of the American Ephemeris and Nautical Almanac (Washington, DC: 1898), pp. 10–11.
International Astronomical Union. «Recommendations Concerning Units». Arxivat de l'original el February 16, 2007. [Consulta: 18 febrer 2007]. Reprinted from the "IAU Style Manual" by G.A. Wilkinson, Comm. 5, in IAU Transactions XXB (1987).
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International Astronomical Union. «Recommendations Concerning Units». Arxivat de l'original el February 16, 2007. [Consulta: 18 febrer 2007]. Reprinted from the "IAU Style Manual" by G.A. Wilkinson, Comm. 5, in IAU Transactions XXB (1987).