Wow, I'm surprised by how much discussion followed from my comments.
I have read your tutorial. I don't know why some people said it
would not be useful. I found it helpful. Perhaps the people who said
that were underestimating how difficult it is for someone to learn
Mizar when starting from zero. I applaud everyone who has written
materials to help new Mizar users. Many thanks, Freek!
As I was learning about Mizar, the one document that helped me the
most was Michal Muzalewski's paper from 1993, "An Outline of PC Mizar".
The paper is still an excellent resource, although it does not
reflect many changes in Mizar that have occurred since 1993. If only
someone had the time to revise that document... If I remember
correctly, I found the paper through a link from Freek's web page.