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In 2011 , the Sumatran elephant has been classified as critically endangered by IUCN as the population has declined by at least 80 % over the last three generations , estimated to be about 75 years .
 IUCN
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 IUCN