What is the relationship between Volkswagen Group and Martin Winterkorn in the context of the input sentence. Choose an answer from: 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.

The EPA Volkswagen Group CEO Martin Winterkorn issued a statement Sunday saying that the company will fully cooperate with government investigations and has ordered an internal probe.
chief_executive_officer