1648
In contrast to the unified character of a European patent application , a granted European patent has , in effect , no unitary character , except for the centralized opposition procedure ( which can be initiated within 9 months from grant , by somebody else than the patent proprietor ) , and the centralized limitation and revocation procedures ( which can only be instituted by the patent proprietor ) .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
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