The animations were made by András Szilágyi, who welcomes suggestions and questions (e-mail: szia@enzim.hu). The animations were made with version 3.7 of the gnuplot graphing program, by giving the appropriate mathematical functions. We used the program under the Linux operating system with Xwindows graphical interface. We created the GIF image files showing individual phases of the animations using the import command in Linux, which makes a snapshot of the gnuplot window and saves it in a file. The individual frames of the animations were put together in animated GIF files using version 1.11.1 of the gifsicle program for making, manipulating and optimizing animated GIF files. This program was used under Linux as well. 30 January 2002 (http://www.enzim.hu/~szia/cddemo/edemo0.htm)