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Additional early works that were important in elucidating the identity and function of radial glia , were completed by Ramón y Cajal , who first suggested that the radial cells were a type of glia through their similarities to astrocytes ; and Wilhelm His , who also proposed the idea that growing axons may use radial cells for orientation and guidance during development .
 Ramón y Cajal, Wilhelm His
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:
 Ramón y Cajal, Wilhelm His