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A number of influential MMORPG designers began as MUD developers and / or players ( such as Raph Koster , Brad McQuaid , Matt Firor , and Brian Green ) or were involved with early MUDs ( like Mark Jacobs and J. Todd Coleman ) .
 Raph Koster, Brad McQuaid, Matt Firor, Brian Green, Mark Jacobs, J. Todd Coleman
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:
 Raph Koster, Brad McQuaid, Matt Firor, Brian Green, Mark Jacobs, J. Todd Coleman