https://cr.yp.to/bib/1995/wirth.pdf
Here's a plain text version on my own blog:
https://liam-on-linux.dreamwidth.org/88032.html
Michael Franz' classic Oberon -- the Overlooked Jewel is also short and highly readable:
https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.90...