Perhaps you should try some spelling variations:
"Hilbert's test problem" » "Hilbert's west problem", "Hilbert's best problem"
"Hilbert's text problem" » "Hilbert's texto problem"
"Hilbert's texth problems" » "Hilbert's textoh problems", "Hilbert's texto problems", "Hilbert's texts problems", "Hilbert's texte problems", "Hilbert's texth problemas", "Hilbert's texth 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 test problem") OR ("Hilbert's text problem"))) OR ("Hilbert's texth problems"))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"Hilbert's test problem\") OR (\"Hilbert's text problem\"))) OR (\"Hilbert's texth problems\"))".
• Removing quotes may allow a broader search: (((( Hilbert's test problem ) OR ( Hilbert's text problem ))) OR ( Hilbert's texth problems )).
• Adding a wildcard symbol may retrieve word variants: (((("Hilbert's test problem") OR ("Hilbert's text problem"))) OR ("Hilbert's texth problems"))*.