Perhaps you should try some spelling variations:
petris » petri (Expand Search), peteris (Expand Search), petriis (Expand Search), petruis (Expand Search)
petrui » petri (Expand Search), petru (Expand Search), peterui (Expand Search), petriui (Expand Search), petruui (Expand Search)
peteri » peterdi (Expand Search), peter (Expand Search), petri (Expand Search)
petr » peter (Expand Search), petri (Expand Search), petru (Expand Search)
petruov » peteruov (Expand Search), petriuov (Expand Search), petruuov (Expand Search), petrov (Expand Search)
petruv » peteruv (Expand Search), petriuv (Expand Search), petruuv (Expand Search), petru (Expand Search), petrov (Expand Search)
petriuv » peteriuv (Expand Search), petriiuv (Expand Search), petruiuv (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 (petrui OR peteri)) OR (petr OR ((petruov OR (petruv OR petriuv)) OR petris))) o.s.~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "fop ((petris OR (petrui OR peteri)) OR (petr OR ((petruov OR (petruv OR petriuv)) OR petris))) o.s.".
• Adding a wildcard symbol may retrieve word variants: fop ((petris OR (petrui OR peteri)) OR (petr OR ((petruov OR (petruv OR petriuv)) OR petris))) o.s.*.