Perhaps you should try some spelling variations:
petrov » petro (Expand Search), petriov (Expand Search), petruov (Expand Search), petroov (Expand Search)
petruoi » petriuoi (Expand Search), petruuoi (Expand Search), petrouoi (Expand Search)
petruou » petriuou (Expand Search), petruuou (Expand Search), petrouou (Expand Search)
petruoou » petriuoou (Expand Search), petruuoou (Expand Search), petrouoou (Expand Search)
petriou » petriiou (Expand Search), petruiou (Expand Search), petroiou (Expand Search)
petr » petri (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 petruoi) OR (((petruou OR petruoou) OR petriou) OR (petr OR peter))) o.s.~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "fop ((petrov OR petruoi) OR (((petruou OR petruoou) OR petriou) OR (petr OR peter))) o.s.*".