1. On Rheticus see: K. H. BURMEISTER: Georg Joachim Rhetikus, 1514–1574. Eine Bio-Bibliographie. 3 vols., Wiesbaden, 1967–1968.
2. On Adriaan van Roomen or Adrianus Romanus (1561–1615), see P. Bockstaele in: Nationaal Biographisch Woordenboeh, vol. 2 (Brussels, 1966), s.v. Roomen, col. 751–765; H. L. L. Busard in: Dictionary of Scientific Biography, vol. 11, pp. 532–534.
3. Rheticus’s letter, the original of which has been lost, was published in Bibliotheca instituta et collecta primum a Conrado Gesnero, deinde in Epitomen redacta et novorum Hbrorum accessione locupletata, jam vero postremo recognita et in duplum post priores editiones aucta, per Josiam Simlerum, Zurich, 1574, p. 228. Romanus took the letter from it, or from the edition Zurich, 1583, p. 270.
4. P. Bockstaele: The Correspondence of Adriaan van Roomen, Lias. Sources and Documents relating to the Early Modern History of Ideas, 3 (1976), 85–129, 249–299 (further cited as Correspondence), letter 1, pp. 94–95.
5. Correspondence, letter 5, pp. 101–102.