50618
This difficulty was notably written about by economists Ludwig von Mises and Friedrich Hayek , who referred to subtly distinct aspects of the problem as the economic calculation problem and local knowledge problem , respectively .
 Ludwig von Mises, Friedrich Hayek
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:
 Ludwig von Mises, Friedrich Hayek