Perhaps you should try some spelling variations:
petris » petri (Expand Search), peteris (Expand Search), petriis (Expand Search), petrois (Expand Search)
petriov » petrov (Expand Search), peteriov (Expand Search), petriiov (Expand Search), petroiov (Expand Search)
petruv » petrov (Expand Search), peteruv (Expand Search), petriuv (Expand Search), petrouv (Expand Search), pentruv (Expand Search), petriv (Expand Search)
petr » peter (Expand Search), petri (Expand Search), petro (Expand Search)
petru » peteru (Expand Search), petriu (Expand Search), petrou (Expand Search), pentru (Expand Search), petri (Expand Search)

Try widening your search to All Fields.

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

• Performing a fuzzy search may retrieve terms with similar spellings: fop ((((petris OR (petriov OR periov)) OR petruv) OR petruv) OR ((petr OR petru) OR per)) o.s.~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "fop ((((petris OR (petriov OR periov)) OR petruv) OR petruv) OR ((petr OR petru) OR per)) o.s.".
• Adding a wildcard symbol may retrieve word variants: fop ((((petris OR (petriov OR periov)) OR petruv) OR petruv) OR ((petr OR petru) OR per)) o.s.*.