Perhaps you should try some spelling variations:
petr » peter (Expand Search), petro (Expand Search), per (Expand Search)
petruv » peteruv (Expand Search), petrouv (Expand Search), peruv (Expand Search), petrov (Expand Search), pentruv (Expand Search)
petriv » peteriv (Expand Search), petroiv (Expand Search), periv (Expand Search), petrov (Expand Search)
petris » peteris (Expand Search), petrois (Expand Search), peris (Expand Search)
petru » peteru (Expand Search), petrou (Expand Search), peru (Expand Search), pentru (Expand Search)
petri » peteri (Expand Search), petroi (Expand Search), peri (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 ((petr OR (petruv OR (petriv OR petris))) OR (petru OR petri)) o.s.~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "fop ((petr OR (petruv OR (petriv OR petris))) OR (petru OR petri)) o.s.".
• Adding a wildcard symbol may retrieve word variants: fop ((petr OR (petruv OR (petriv OR petris))) OR (petru OR petri)) o.s.*.