Prevent potential bugs when using instance of and sparql #153
Description
The first problem is that the zbmath importer sets all items as scholarly article, so if someone sets them as something else manually, they will not be found anymore. The reason why we search as instance of is because the item might not be there in sparql yet. Also, sparql is generally slow. It might be the solution to use haswbstatement as a general rule, which would solve both problems.