How to use this website

This website opbs.de works like a book, by allowing you to flip through it.

There are clickable areas at the right and left edges for the next and previous page. These active zones appear if you hover the mouse cursor over them.

The top of each page has a breadcrumb navigation to keep track of your location within the website. Additional language versions of the site – if available – can also be selected.

The bottom of each page has navigational links for the previous page, next page and start of page.

Links and cross-references are denoted with small caps. They change their colour by roll-over.

Links to outside material are denoted additionally with a coloured arrow↗.