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Other forthcoming measurements , such as those of 21 centimeter radiation ( radiation emitted and absorbed from neutral hydrogen before the first stars formed ) , may measure the power spectrum with even greater resolution than the CMB and galaxy surveys , although it is not known if these measurements will be possible or if interference with radio sources on Earth and in the galaxy will be too great .
 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