Perhaps you should try some spelling variations:
petro » petrov (Expand Search), petri (Expand Search), petero (Expand Search), petrio (Expand Search), pero (Expand Search)
peru » per (Expand Search)
petriov » peteriov (Expand Search), petriiov (Expand Search), periov (Expand Search)
petruv » peteruv (Expand Search), petriuv (Expand Search), peruv (Expand Search)
petriuv » peteriuv (Expand Search), petriiuv (Expand Search), periuv (Expand Search)
petru » peteru (Expand Search), petriu (Expand Search), peru (Expand Search)
petr » peter (Expand Search), petri (Expand Search), per (Expand Search)

Try widening your search to All Fields.

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

• Performing a fuzzy search may retrieve terms with similar spellings: fop ((petriov OR (petruv OR petriuv)) OR (((petro OR pero) OR (petru OR peru)) OR petr)) o.s.~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "fop ((petriov OR (petruv OR petriuv)) OR (((petro OR pero) OR (petru OR peru)) OR petr)) o.s.".
• Adding a wildcard symbol may retrieve word variants: fop ((petriov OR (petruv OR petriuv)) OR (((petro OR pero) OR (petru OR peru)) OR petr)) o.s.*.