Perhaps you should try some spelling variations:
petriov » petrov (Expand Search), petruiov (Expand Search), petroiov (Expand Search), periov (Expand Search)
petrv » petrov (Expand Search), petru (Expand Search), petro (Expand Search), petruv (Expand Search), perv (Expand Search)
petero » peters (Expand Search), petro (Expand Search)
petr » petru (Expand Search), petro (Expand Search), per (Expand Search)
petri » petrui (Expand Search), petroi (Expand Search), peri (Expand Search)
petroi » petruoi (Expand Search), petrooi (Expand Search), peroi (Expand Search), petro (Expand Search), petrov (Expand Search), petrow (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 ((petriov OR petrv) OR ((perio OR petero) OR (((petr OR petri) OR petroi) OR peter))) o.s.~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "fop ((petriov OR petrv) OR ((perio OR petero) OR (((petr OR petri) OR petroi) OR peter))) o.s.".
• Adding a wildcard symbol may retrieve word variants: fop ((petriov OR petrv) OR ((perio OR petero) OR (((petr OR petri) OR petroi) OR peter))) o.s.*.