ABSTRACT
This chapter seems, at first glance, to be more difficult than the previous ones, and we all like to avoid difficulties. Keeping this in mind, the authors would like to begin this chapter with a story of a man whose doctor gravely prescribed him a gymnastics regimen. Not wanting to do the exercises, the lazy patient made an agreement with himself: “OK, I’ll exercise once a week, and then we’ll see.” So he got up in the morning, begrudgingly gathered all his will, and started doing gymnastics, comforted by the thought that once it is done, he will live a free man for a week. Upon finishing the thought and the exercise, the man was pleased and at ease.
