Perhaps you should try some spelling variations:
perv » per (Expand Search)
peru » petru (Expand Search), per (Expand Search)
petruov » peteruov (Expand Search), petruuov (Expand Search), petrouov (Expand Search)
petriv » peteriv (Expand Search), petruiv (Expand Search), petroiv (Expand Search)
petri » peteri (Expand Search), petrui (Expand Search), petroi (Expand Search)
petroi » peteroi (Expand Search), petruoi (Expand Search), petrooi (Expand Search)
petr » peter (Expand Search), petru (Expand Search), petro (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 ((((petruov OR periov) OR petriv) OR perv) OR ((peru OR (petri OR petroi)) OR petr)) o.s.~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "fop ((((petruov OR periov) OR petriv) OR perv) OR ((peru OR (petri OR petroi)) OR petr)) o.s.".
• Adding a wildcard symbol may retrieve word variants: fop ((((petruov OR periov) OR petriv) OR perv) OR ((peru OR (petri OR petroi)) OR petr)) o.s.*.