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