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Within this framework , W. A. Stewart defined a " language " as an autonomous variety together with all the varieties that are heteronomous with respect to it , noting that an essentially equivalent definition had been stated by Charles A. Ferguson and John J. Gumperz in 1960 .
 W. A. Stewart, Charles A. Ferguson, John J. Gumperz
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:
 W. A. Stewart, Charles A. Ferguson, John J. Gumperz