Useful Websites

This collection of links contains only websites that I consider very valuable for orientation and research. I try to keep the list short; it is sorted by category. Click on each category to open or close the list of links. (There are additional Website recommendations in some of the main content pages. )

[wp-blogroll orderby=name showdesc=1 showbrk=1 order=ASC show_rss=1 showhide=1]