Perhaps you should try some spelling variations:
tenis » tesis, denis, tenia
tenti » texti, kenti, teni
tent » text, kent, ten
test » text, west, best
problem » problema, problemas
problems » problemas, problemass, problema
problemsas » problemasas, problemassas, problemaas, problemas, problema, problemes

You may be able to get more results by adjusting your search query.

• The words AND, OR and NOT may confuse the search; try adding quotes: "Hilbert's ((tenti OR tenis) OR (tent OR test)) ((problem OR problems) OR problemsas)~".
• Adding a wildcard symbol may retrieve word variants: Hilbert's ((tenti OR tenis) OR (tent OR test)) ((problem OR problems) OR problemsas)*.