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