Perhaps you should try some spelling variations:
petrov » peterov (Expand Search), petriov (Expand Search), petruov (Expand Search)
petriov » peteriov (Expand Search), petriiov (Expand Search), petruiov (Expand Search)
petrui » peterui (Expand Search), petriui (Expand Search), petruui (Expand Search)
petroi » peteroi (Expand Search), petrioi (Expand Search), petruoi (Expand Search)
petruoui » peteruoui (Expand Search), petriuoui (Expand Search), petruuoui (Expand Search)
petr » peter (Expand Search), petri (Expand Search), petru (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 (petriov OR peteriiov)) OR (((petrui OR petroi) OR petruoui) OR petr)) o.s.~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "fop ((petrov OR (petriov OR peteriiov)) OR (((petrui OR petroi) OR petruoui) OR petr)) o.s.*".