He was an early investor in Berkshire Hathaway , Warren Buffett 's holding company , and served on Citigroup 's board .
Berkshire Hathaway /business/company/major_shareholders Warren Buffett
Warren Buffett /business/company_shareholder/major_shareholder_of Berkshire Hathaway
Warren Buffett /business/person/company Berkshire Hathaway
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Berkshire Hathaway
ORGANIZATION
Warren Buffett
PERSON
/business/company/major_shareholders
Warren Buffett
PERSON
Berkshire Hathaway
ORGANIZATION
/business/company_shareholder/major_shareholder_of
Warren Buffett
PERSON
Berkshire Hathaway
ORGANIZATION
/business/person/company