== See also ==* Celestial spheres* Firmament* Unmoved mover==References====Further reading==* J. Barnes, "Aristotle" (1982)* M. A. Orr, "Dante and the Medieval Astronomers" (1956)* Thomas Kuhn, "The Copernican Revolution" (1957)== External links ==* The Geocentric or Ptolemaic Notion of the Universe
* J. Barnes, "Aristotle" (1982)* M. A. Orr, "Dante and the Medieval Astronomers" (1956)* Thomas Kuhn, "The Copernican Revolution" (1957)* The Geocentric or Ptolemaic Notion of the Universe