Perhaps you should try some spelling variations:
petruow » petrow (Expand Search), peteruow (Expand Search), petruuow (Expand Search), petrouow (Expand Search)
petri » peteri (Expand Search), petrui (Expand Search), petroi (Expand Search)
petrooi » peterooi (Expand Search), petruooi (Expand Search), petroooi (Expand Search)
petr » peter (Expand Search), petru (Expand Search), petro (Expand Search)
petriov » peteriov (Expand Search), petruiov (Expand Search), petroiov (Expand Search), petrov (Expand Search)
petruv » peteruv (Expand Search), petruuv (Expand Search), petrouv (Expand Search), petru (Expand Search), petrov (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 ((petri OR (petruow OR (petruow OR petrooi))) OR (petr OR ((petriov OR petruv) OR petri))) o.s.~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "fop ((petri OR (petruow OR (petruow OR petrooi))) OR (petr OR ((petriov OR petruv) OR petri))) o.s.".
• Adding a wildcard symbol may retrieve word variants: fop ((petri OR (petruow OR (petruow OR petrooi))) OR (petr OR ((petriov OR petruv) OR petri))) o.s.*.