Perhaps you should try some spelling variations:
"Hilbert's abierto problema" » "Hilbert's tierra problema", "Hilbert's viejo problema"
"Hilbert's tent problem" » "Hilbert's tenti problem", "Hilbert's text problem", "Hilbert's test problem"
"Hilbert's teets problems" » "Hilbert's tenets problems", "Hilbert's tweets problems", "Hilbert's texts problems", "Hilbert's teets problemas"

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 tent problem") OR ("Hilbert's abierto problema"))) OR ("Hilbert's teets problems"))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"Hilbert's tent problem\") OR (\"Hilbert's abierto problema\"))) OR (\"Hilbert's teets problems\"))".
• Removing quotes may allow a broader search: (((( Hilbert's tent problem ) OR ( Hilbert's abierto problema ))) OR ( Hilbert's teets problems )).
• Adding a wildcard symbol may retrieve word variants: (((("Hilbert's tent problem") OR ("Hilbert's abierto problema"))) OR ("Hilbert's teets problems"))*.