60997
This period also saw several other historic developments including the introduction of the first practical magnetic sound recording system , the magnetic wire recorder , which was based on the work of Danish inventor Valdemar Poulsen .
 person: Valdemar Poulsen
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: Valdemar Poulsen 
Answer:
 person: Valdemar Poulsen