Perhaps you should try some spelling variations:
petrov » peterov (Expand Search), petruov (Expand Search), petroov (Expand Search)
petriiov » peteriiov (Expand Search), petruiiov (Expand Search), petroiiov (Expand Search)
petruv » peteruv (Expand Search), petruuv (Expand Search), petrouv (Expand Search)
petri » peteri (Expand Search), petrui (Expand Search), petroi (Expand Search)
petroi » peteroi (Expand Search), petruoi (Expand Search), petrooi (Expand Search)
petr » peter (Expand Search), petru (Expand Search), petro (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 petriiov) OR petruv) OR (((petri OR petroi) OR (peteru OR per)) OR petr)) o.s.~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "fop (((petrov OR petriiov) OR petruv) OR (((petri OR petroi) OR (peteru OR per)) OR petr)) o.s.*".