Perhaps you should try some spelling variations:
petrov » petro (Expand Search), petruov (Expand Search), petroov (Expand Search), perov (Expand Search)
petris » petruis (Expand Search), petrois (Expand Search), peris (Expand Search)
petrois » petruois (Expand Search), petroois (Expand Search), perois (Expand Search)
petr » petru (Expand Search), petro (Expand Search), per (Expand Search)
petri » petrui (Expand Search), petroi (Expand Search), peri (Expand Search)
peteru » petru (Expand Search), peters (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 petrov) OR ((petris OR petrois) OR (((petr OR peter) OR peteru) OR petri))) o.s.~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "fop ((petrov OR petrov) OR ((petris OR petrois) OR (((petr OR peter) OR peteru) OR petri))) o.s.*".