Perhaps you should try some spelling variations:
petriov » petrov (Expand Search), petriiov (Expand Search), petroiov (Expand Search), periov (Expand Search)
petrui » petri (Expand Search), pentrui (Expand Search), petrii (Expand Search), petriui (Expand Search), petroui (Expand Search), perui (Expand Search)
petris » petri (Expand Search), petriis (Expand Search), petrois (Expand Search), peris (Expand Search)
petru » pentru (Expand Search), petri (Expand Search), petriu (Expand Search), petrou (Expand Search), peru (Expand Search)
petriii » petriiii (Expand Search), petroiii (Expand Search), periii (Expand Search)
petr » petri (Expand Search), petro (Expand Search), per (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 ((petriov OR ((petrui OR (petris OR petriii)) OR petru)) OR (petr OR peter)) o.s.~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "fop ((petriov OR ((petrui OR (petris OR petriii)) OR petru)) OR (petr OR peter)) o.s.".
• Adding a wildcard symbol may retrieve word variants: fop ((petriov OR ((petrui OR (petris OR petriii)) OR petru)) OR (petr OR peter)) o.s.*.