Perhaps you should try some spelling variations:
petriov » petrov (Expand Search), petriv (Expand Search), petriiov (Expand Search), petruiov (Expand Search), petroiov (Expand Search)
petroiv » petrov (Expand Search), petrioiv (Expand Search), petruoiv (Expand Search), petrooiv (Expand Search)
petrio » petri (Expand Search), petro (Expand Search), petriio (Expand Search), petruio (Expand Search), petroio (Expand Search)
petris » petri (Expand Search), petriis (Expand Search), petruis (Expand Search), petrois (Expand Search)
petr » petri (Expand Search), petru (Expand Search), petro (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 petroiv) OR ((((petrio OR periio) OR periio) OR petris) OR (petr OR peter))) o.s.~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "fop ((petriov OR petroiv) OR ((((petrio OR periio) OR periio) OR petris) OR (petr OR peter))) o.s.".
• Adding a wildcard symbol may retrieve word variants: fop ((petriov OR petroiv) OR ((((petrio OR periio) OR periio) OR petris) OR (petr OR peter))) o.s.*.