4220
Background Often student riots are political in nature , such as those that were common in the US and Western Europe during the Vietnam War era , although student riots can occur as a result of peaceful demonstration oppressed by the authorities and after sporting events ( hooliganism ) .
 None
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
 Entities:  
Answer:
 None