SOURCES AND REFERENCES.

.on the web: mathematics.

• GNU GSL Scientific Library Gerard Jungman.
• numericana(..)ellipse Gérard P. Michon.
• mathforum(..)ellipse Dr.Math - answer by Robert L. Ward.
• mathworld/Ellipse Eric W. Weisstein.
• jcalvert(..)ellipse James B. Calvert, University of Denver.
• mathworld/Hyperbola Eric W. Weisstein.

.on paper: mathematics, astronomy, programming.

• "Efficient C Programming", by Mark Allen Weiss, Prentice Hall, 1995.
• "Mathematics", by A. D. Aleksandrov, A. N. Kolmogorov, M. A. Lavrent'ev. Moscow, 1956, by U.S.S.R. Accademy of Science. Italian Edition: Torino, 1974 by Boringhieri.
• "e: history of a number" by Eli Maor, Princeton University Press, ninth printing, 1998.
• "Ramanujan and Pi" by Johnathan Borwein and Peter Borwein, included in: "PI: A Source Book", by Johnathan Borwein, Peter Borwein and Lennart Berggren, Springer Verlag, 1997, ISBN: 0-387-94924-0.
• "Digital Signal Processing" by A.V. Oppenheim and R.W. Shafer, Prentice Hall, 1975. Second Italian Edition: Milano, 1983, Franco Angeli.
• "La Cometa di Halley" by Cesare Barbieri, included in: "Le Comete nell'Astronomia Moderna - Il prossimo incontro con la Cometa di Halley" by Universita' degli Studi di Napoli, Guida Editori, Napoli, 1983.