67887
In 1873 Nikolay Umov pointed out a relation between mass and energy for ether in the form of , where .
 Nikolay Umov
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 Nikolay Umov