Perhaps you should try some spelling variations:
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)
petroou » peteroou (Expand Search), petruoou (Expand Search), petrooou (Expand Search)
petruui » peteruui (Expand Search), petruuui (Expand Search), petrouui (Expand Search)
petruuui » peteruuui (Expand Search), petruuuui (Expand Search), petrouuui (Expand Search)
peteri » peterdi (Expand Search), peter (Expand Search), peters (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 ((petris OR petri) OR ((((petr OR petroou) OR (petruui OR petruuui)) OR peteri) OR per)) o.s.~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "fop ((petris OR petri) OR ((((petr OR petroou) OR (petruui OR petruuui)) OR peteri) OR per)) o.s.".
• Adding a wildcard symbol may retrieve word variants: fop ((petris OR petri) OR ((((petr OR petroou) OR (petruui OR petruuui)) OR peteri) OR per)) o.s.*.