Perhaps you should try some spelling variations:
petro » petrov (Expand Search), petri (Expand Search), petru (Expand Search), petero (Expand Search), petrio (Expand Search), petruo (Expand Search)
petriv » peteriv (Expand Search), petriiv (Expand Search), petruiv (Expand Search)
petruuv » peteruuv (Expand Search), petriuuv (Expand Search), petruuuv (Expand Search)
petruo » peteruo (Expand Search), petriuo (Expand Search), petruuo (Expand Search)
petruio » peteruio (Expand Search), petriuio (Expand Search), petruuio (Expand Search)
petr » peter (Expand Search), petri (Expand Search), petru (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 ((petriv OR petruuv) OR (peteru OR ((((petro OR petruo) OR petero) OR petruio) OR petr))) o.s.~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "fop ((petriv OR petruuv) OR (peteru OR ((((petro OR petruo) OR petero) OR petruio) OR petr))) o.s.".
• Adding a wildcard symbol may retrieve word variants: fop ((petriv OR petruuv) OR (peteru OR ((((petro OR petruo) OR petero) OR petruio) OR petr))) o.s.*.