Perhaps you should try some spelling variations:
petriv » petri (Expand Search), petrov (Expand Search), petriiv (Expand Search), petruiv (Expand Search), petroiv (Expand Search)
petruiv » petriuiv (Expand Search), petruuiv (Expand Search), petrouiv (Expand Search)
petr » petri (Expand Search), petru (Expand Search), petro (Expand Search)
petroi » petrioi (Expand Search), petruoi (Expand Search), petrooi (Expand Search), petri (Expand Search), petro (Expand Search), petrov (Expand Search)
petris » petriis (Expand Search), petruis (Expand Search), petrois (Expand Search), petri (Expand Search)
petriis » petriiis (Expand Search), petruiis (Expand Search), petroiis (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 petruiv) OR (((petr OR petroi) OR ((petris OR petriis) OR perio)) OR peter)) o.s.~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "fop ((petriv OR petruiv) OR (((petr OR petroi) OR ((petris OR petriis) OR perio)) OR peter)) o.s.".
• Adding a wildcard symbol may retrieve word variants: fop ((petriv OR petruiv) OR (((petr OR petroi) OR ((petris OR petriis) OR perio)) OR peter)) o.s.*.