David Galadí Enríquez, Enric Marco Soler, Vicent Josep Martínez García, Joan Antoni Miralles Torres. Astronomía fundamental. Universitat de València, 2011. p. 38 de 320. ISBN9788437086439. Consultado el 28 de abril de 2018.
galileo.rice.edu The Galileo Project > Science > The Telescope by Al Van Helden "The Hague discussed the patent applications first of Hans Lipperhey of Middelburg, and then of Jacob Metius of Alkmaar... another citizen of Middelburg, Sacharias Janssen had a telescope at about the same time but was at the Frankfurt Fair where he tried to sell it"
