Perhaps you should try some spelling variations:
gramatica comparada » gramatica comparativa
"gramatica comparado de general" » "gramatica comparativa de general", "gramatica comparativo de general", "gramatica comparacion de general", "gramatica comparado del general", "gramatica comparado de genero", "gramatica comparado _ general"
"Gramática comparada ley general" » "Gramática comparada de general", "Gramática comparada y general", "Gramática comparada e general", "Gramática comparada leyes general"

Try widening your search to All Fields.

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• Performing a fuzzy search may retrieve terms with similar spellings: (("Gramática comparada ley general") or ("gramatica comparado de general"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("Gramática comparada ley general") OR ("gramatica comparado de general")).
• Removing quotes may allow a broader search: (( Gramática comparada ley general ) or ( gramatica comparado de general )).
• Adding a wildcard symbol may retrieve word variants: (("Gramática comparada ley general") or ("gramatica comparado de general"))*.