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The 1797 Riobamba earthquake , which caused up to 40,000 casualties , was studied by Alexander von Humboldt , when he visited the area in 1801 – 1802 .
 Riobamba earthquake, Alexander von Humboldt
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Riobamba earthquake, Alexander von Humboldt