Utilize the input text as a context reference, choose the right relationship between Berkshire Hathaway and Phillips 66 from the options. Options: product/material produced, manufacturer, distributed by, industry, position held, original broadcaster, owned by, founded by, distribution format, headquarters location, stock exchange, currency, parent organization, chief executive officer, director/manager, owner of, operator, member of, employer, chairperson, platform, subsidiary, legal form, publisher, developer, brand, business division, location of formation, creator.

Phillips 66 was up 3.5 percent at $79.97 after Warren Buffett's Berkshire Hathaway disclosed a $4.48 billion stake in the oil refiner.

Answer: owner_of