Perhaps you should try some spelling variations:
vulgareiae » bulgariae, vulgarise
bulgerian » bulgarian, bulgarians, bulgarien
ungarische » ungarischen
bulgaria » bulgareia, vulgaria, bulgeria
bulgar » bulgare, vulgar, bulger

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: (((vulgareiae OR (bulgerian OR eulerian)) OR (ungarische OR bulgaria)) OR (bulgar OR bulge)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(((vulgareiae or (bulgerian OR eulerian)) or (ungarische or bulgaria)) or (bulgar or bulge))".
• Adding a wildcard symbol may retrieve word variants: (((vulgareiae or (bulgerian OR eulerian)) or (ungarische or bulgaria)) or (bulgar or bulge))*.