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Guitarist Steve Vai ( who co-produced Skyscraper and wrote a majority of its songs ) and bassist  Billy Sheehan  who formed the core of  David Lee Roth  's solo band left the group over various controversies regarding Skyscraper .
 None
Given a phrase that describes the relationship between two words, extract the words and the lexical relationship between them. The output format should be "relation1: word1, word2; relation2: word3, word4". 
Option: cities of residence, top members employees, members, alternate names, origin, state or provinces of residence, title of person, spouse, city of headquarters, NA, founded by, state or province of headquarters, employee of, countries of residence, country of birth, founded, subsidiaries, country of headquarters 
Text: {0} 
Answer:
 NA: Billy Sheehan, David Lee Roth