8521
WAAS uses a network of ground-based reference stations , in North America and Hawaii , to measure small variations in the GPS satellites ' signals in the western hemisphere .
 location: North America; location: Hawaii
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:
 location: North America; location: Hawaii