Perhaps you should try some spelling variations:
perov » petrov (Expand Search)
petruov » peteruov (Expand Search), petruuov (Expand Search), petrouov (Expand Search)
petri » peteri (Expand Search), petrui (Expand Search), petroi (Expand Search)
petroi » peteroi (Expand Search), petruoi (Expand Search), petrooi (Expand Search)
petriio » peteriio (Expand Search), petruiio (Expand Search), petroiio (Expand Search)
petrui » peterui (Expand Search), petruui (Expand Search), petroui (Expand Search)
petruiui » peteruiui (Expand Search), petruuiui (Expand Search), petrouiui (Expand Search)
petr » peter (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 ((petruov OR perov) OR ((((petri OR petroi) OR petriio) OR (petrui OR petruiui)) OR petr)) o.s.~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "fop ((petruov OR perov) OR ((((petri OR petroi) OR petriio) OR (petrui OR petruiui)) OR petr)) o.s.".
• Adding a wildcard symbol may retrieve word variants: fop ((petruov OR perov) OR ((((petri OR petroi) OR petriio) OR (petrui OR petruiui)) OR petr)) o.s.*.