Given the input sentence, please extract the subject and object containing a certain relation in the sentence according to the following relation types, in the format of "relation1: word1, word2; relation2: word3, word4". Relations include: 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.

Legendary US investor Warren Buffett -- in a 2011 letter to shareholders of his Berkshire Hathaway investment group -- famously compared the entire world's gold stock of 170,000 metric tons, valued at $9.6 trillion (pile A) with another set of assets costing an equal amount (pile B).

Answer: owned_by: Berkshire Hathaway, Warren Buffett; chief_executive_officer: Berkshire Hathaway, Warren Buffett; director_/_manager: Berkshire Hathaway, Warren Buffett; owner_of: Warren Buffett, Berkshire Hathaway; chairperson: Berkshire Hathaway, Warren Buffett