188792
Hoping for a reward , Kark killed the wanted earl and brought his head to enemy Olaf Tryggvason , later king of Norway .
 Kark, Olaf Tryggvason
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Kark, Olaf Tryggvason