80207
The strategos of Thessalonica is attested for the first time in 836 , but a letter of Emperor Michael II ( r. 820 – 829 ) to the Frankish king Louis the Pious ( r. 814 – 840 ) may indicate the theme 's existence already in 824 .
 Thessalonica, Michael II, Louis the Pious
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Thessalonica, Michael II, Louis the Pious