1871
Later , Niels Henrik Abel discussed the subject in a memoir , treating notably questions of convergence .
 person: Niels Henrik Abel
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 person: Niels Henrik Abel