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 rose 2.38 percent after Warren Buffett's Berkshire Hathaway disclosed a $4.48 billion stake in the oil refiner.

Answer: owner_of