Perhaps you should try some spelling variations:
petriov » petrov (Expand Search), peteriov (Expand Search), petruiov (Expand Search), petroiov (Expand Search)
petrou » petru (Expand Search), petro (Expand Search), petrov (Expand Search), peterou (Expand Search), petruou (Expand Search), petroou (Expand Search)
petris » peteris (Expand Search), petruis (Expand Search), petrois (Expand Search)
petri » peteri (Expand Search), petrui (Expand Search), petroi (Expand Search)
petr » peter (Expand Search), petru (Expand Search), petro (Expand Search)
petroi » peteroi (Expand Search), petruoi (Expand Search), petrooi (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 ((peroov OR petriov) OR ((petrou OR (petris OR petri)) OR (petr OR (petroi OR peterdi)))) o.s.~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "fop ((peroov OR petriov) OR ((petrou OR (petris OR petri)) OR (petr OR (petroi OR peterdi)))) o.s.".
• Adding a wildcard symbol may retrieve word variants: fop ((peroov OR petriov) OR ((petrou OR (petris OR petri)) OR (petr OR (petroi OR peterdi)))) o.s.*.