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His son Dirk was still a boy at this time , but Arnulf 's widow Luitgard managed to retain the county for her son with support from first Emperor Otto III and later her brother-in-law , Emperor Henry II .
 Dirk, Arnulf, Emperor Otto III, Emperor Henry II
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Dirk, Arnulf, Emperor Otto III, Emperor Henry II