Perhaps you should try some spelling variations:
petriov » peteriov (Expand Search), petriiov (Expand Search), petruiov (Expand Search)
petruov » peteruov (Expand Search), petriuov (Expand Search), petruuov (Expand Search)
petruiu » peteruiu (Expand Search), petriuiu (Expand Search), petruuiu (Expand Search)
petroi » peteroi (Expand Search), petrioi (Expand Search), petruoi (Expand Search)
petruo » peteruo (Expand Search), petriuo (Expand Search), petruuo (Expand Search)
petriuo » peteriuo (Expand Search), petriiuo (Expand Search), petruiuo (Expand Search)
petr » peter (Expand Search), petri (Expand Search), petru (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 petruov) OR (petruiu OR ((petroi OR (petruo OR petriuo)) OR petr))) o.s.~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "fop ((petriov OR petruov) OR (petruiu OR ((petroi OR (petruo OR petriuo)) OR petr))) o.s.".
• Adding a wildcard symbol may retrieve word variants: fop ((petriov OR petruov) OR (petruiu OR ((petroi OR (petruo OR petriuo)) OR petr))) o.s.*.