Resources
Electronic Sources
- Home Page 3.0. Filemaker, Inc. USA.
various images. 1995.
- Graph Power. Ventura Educational
Systems. Grover Beach, CA. 1994.
- Kid Pix. Broderbund Software, Inc. USA.
1991.
Printed material
- Drum, W., Dr. Imagines Demonstrandae.
Berlin, Germany. The "Quintessenz". 1970.