↑https://theguardian.com/science/blog/2009/aug/25/galileos-telescope-400-years-anniversary: "on 25 August 1609, the Italian astronomer and philosopher Galilei Galileo showed Venetian merchants his new creation, a telescope" ("el 25 de agosto de 1609, el astrónomo y filósofo italiano Galilei Galileo mostró a los comerciantes venecianos su nueva creación, un telescopio")
↑ abhttps://www.scientificamerican.com/article/galileo-kepler-iya: "Four hundred years ago... was the publication of Johannes Kepler's Astronomia Nova (The New Astronomy) in 1609, a treatise in which the German astronomer introduced the first two of his laws describing planetary motion." ("Hace cuatrocientos años... fue la publicación de Astronomia Nova (La nueva astronomía) de Johannes Kepler en 1609, un tratado en el que el astrónomo alemán introdujo las dos primeras de sus leyes que describen el movimiento planetario.")
↑Michael Rheta Martin and Richard C. Harrier, The Concise Encyclopedic Guide to Shakespeare, Discus Books (publicado por Avon), New York, 1971, p. 327: "Troilus and Cressida, The Tragedy of, written 1598-1602; registered 1603; published 1609"
↑Marchette Chute, Shakespeare of London, E. P. Dutton and Company, New York, 1949, pp. 287-288
↑The World Book Encyclopedia, World Book, Chicago, edição de 2014, Tomo 17 (S-Sn), p. 362: "Troilus and Cressida... was probably first performed in 1602 and first published in 1609."