1. http://www.enjoythemusic.com/cartridgehistory.htm
2. Shan X. Wang, A. M. Taratorin, Magnetic Information Storage Technology (Academic Press, San Diego, 1999), Chapter 1.
3. S. Khizroev, D. Litvinov, J. Appl. Phys. 95(9), 4521–4537 (2004).
4. http://www.sims.berkeley.edu/research/projects/how-much-info/
5. http://nobelprize.org/physics/educational/microscopes/scanning/