Perhaps you should try some spelling variations:
petrov » petro (Expand Search), petruov (Expand Search), petroov (Expand Search), perov (Expand Search)
petruov » petruuov (Expand Search), petrouov (Expand Search), peruov (Expand Search)
petr » petru (Expand Search), petro (Expand Search), per (Expand Search)
petrio » petruio (Expand Search), petroio (Expand Search), perio (Expand Search), petris (Expand Search), petro (Expand Search)
petruiio » petruuiio (Expand Search), petrouiio (Expand Search), peruiio (Expand Search)
petri » petrui (Expand Search), petroi (Expand Search), peri (Expand Search)

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: fop (((petrov OR perov) OR petruov) OR (((petr OR peter) OR (petrio OR petruiio)) OR petri)) o.s.~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "fop (((petrov OR perov) OR petruov) OR (((petr OR peter) OR (petrio OR petruiio)) OR petri)) o.s.*".