Perhaps you should try some spelling variations:
"Hilbert's testh problem" » "Hilbert's test problem", "Hilbert's testa problem", "Hilbert's tests problem"
"Hilbert's tent problem" » "Hilbert's tenti problem", "Hilbert's text problem", "Hilbert's test problem"
"Hilbert's tenth problems" » "Hilbert's tentih problems", "Hilbert's texth problems", "Hilbert's testh problems", "Hilbert's tenti problems", "Hilbert's benth problems", "Hilbert's teeth problems", "Hilbert's tenth problemas", "Hilbert's tenth problema"

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

• Performing a fuzzy search may retrieve terms with similar spellings: (((("Hilbert's testh problem") OR ("Hilbert's tent problem"))) OR ("Hilbert's tenth problems"))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"Hilbert's testh problem\") OR (\"Hilbert's tent problem\"))) OR (\"Hilbert's tenth problems\"))".
• Removing quotes may allow a broader search: (((( Hilbert's testh problem ) OR ( Hilbert's tent problem ))) OR ( Hilbert's tenth problems )).
• Adding a wildcard symbol may retrieve word variants: (((("Hilbert's testh problem") OR ("Hilbert's tent problem"))) OR ("Hilbert's tenth problems"))*.