My grateful thanks to Sarah Jane Webb for her translation of the material posted here. Indeed, she translated in English something I wrote, but not this presentation (if you find mistakes in it, the fault is only mine).

I decided to post all this because I noticed that a number of  people visiting this site is living out of Italy; I don’t know if you are English speakers or not, but I feel Italian can be hard to understand to some of you.

This section includes: