Perhaps you should try some spelling variations:
petro » petrov (Expand Search), petri (Expand Search), petero (Expand Search), petrio (Expand Search), pero (Expand Search)
petriov » peteriov (Expand Search), petriiov (Expand Search), periov (Expand Search)
petriv » peteriv (Expand Search), petriiv (Expand Search), periv (Expand Search)
petru » peteru (Expand Search), petriu (Expand Search), peru (Expand Search)
petrio » peterio (Expand Search), petriio (Expand Search), perio (Expand Search)
petr » peter (Expand Search), petri (Expand Search), per (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 petriv) OR (petru OR ((petro OR petrio) OR petr))) o.s.~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "fop ((petriov OR petriv) OR (petru OR ((petro OR petrio) OR petr))) o.s.".
• Adding a wildcard symbol may retrieve word variants: fop ((petriov OR petriv) OR (petru OR ((petro OR petrio) OR petr))) o.s.*.