Perhaps you should try some spelling variations:
perov » petrov (Expand Search)
peru » petru (Expand Search), per (Expand Search)
petruov » peteruov (Expand Search), petriuov (Expand Search), petruuov (Expand Search)
petriov » peteriov (Expand Search), petriiov (Expand Search), petruiov (Expand Search)
petruo » peteruo (Expand Search), petriuo (Expand Search), petruuo (Expand Search)
petruiuv » peteruiuv (Expand Search), petriuiuv (Expand Search), petruuiuv (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 ((petruov OR petriov) OR ((((petruo OR perov) OR peru) OR petruiuv) OR petr)) o.s.~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "fop ((petruov OR petriov) OR ((((petruo OR perov) OR peru) OR petruiuv) OR petr)) o.s.".
• Adding a wildcard symbol may retrieve word variants: fop ((petruov OR petriov) OR ((((petruo OR perov) OR peru) OR petruiuv) OR petr)) o.s.*.