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It was constructed in the years 15 to 16 bcThe theater has undergone several renovations , such as at the end of the 1st century or early 2nd century , possibly during the reign of Emperor Trajan , when the current facade of the scaenae frons was erected , and another in the time of Constantine I ( between 330 and 340 ) , introducing new decorative-architectural elements and a walkway around the monument .
 Trajan, Constantine I
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Trajan, Constantine I