Perhaps you should try some spelling variations:
perov » petrov (Expand Search)
petruov » peteruov (Expand Search), petruuov (Expand Search), petrouov (Expand Search)
petroou » peteroou (Expand Search), petruoou (Expand Search), petrooou (Expand Search)
petri » peteri (Expand Search), petrui (Expand Search), petroi (Expand Search)
petroui » peteroui (Expand Search), petruoui (Expand Search), petrooui (Expand Search)
petriui » peteriui (Expand Search), petruiui (Expand Search), petroiui (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 ((((petroou OR pero) OR petri) OR (petroui OR petriui)) OR petr)) o.s.~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "fop ((petruov OR perov) OR ((((petroou OR pero) OR petri) OR (petroui OR petriui)) OR petr)) o.s.".
• Adding a wildcard symbol may retrieve word variants: fop ((petruov OR perov) OR ((((petroou OR pero) OR petri) OR (petroui OR petriui)) OR petr)) o.s.*.