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A further high point in Schäffer 's career was the employment as one of several cameramen in Walter Ruttmann 's experimental documentary film Berlin : Symphony of a Great City ( 1927 ) .
 Schäffer, Walter Ruttmann, Berlin
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Schäffer, Walter Ruttmann, Berlin