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Krasinsky, G. A.; Novikov, F. A.; Scripnichenko, V. I. (1989). "Problem Oriented Language for Ephemeris Astronomy and Its Realisation in the System ERA". Applications of Computer Technology to Dynamical Astronomy. pp. 219–229. doi:10.1007/978-94-009-0985-4_37. ISBN978-94-010-6932-8. S2CID123340575.