61551
In the 1960 s , because the majority of the residents of the federal capital were illiterate , the planners of the Mexico City Metro designed a system of unique icons to identify each station in the system in addition to its formal name .
 Mexico City Metro
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Mexico City Metro