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At first Walter was surprised with the youthfulness of the architect , until he visited one of the houses Mackintosh had previously designed and was convinced that this was the right person to build his home .
 Walter, Mackintosh
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Walter, Mackintosh