364203
At the end of the 1970s , Elizabeth found she was able to refine the technique and successfully strengthen the voices of hard rock and heavy metal music vocalists who often sung with vigorous screams and yells .
 Elizabeth
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Elizabeth