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After he explains how it works ( including a " non-return key " that keeps the machine at the traveler 's destination and a " vaporizing equalizer " that keeps the traveler and machine on equal terms ) , police constables arrive at the house searching for Jack the Ripper .
 person: Jack the Ripper
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 person: Jack the Ripper