He argues that investors are not only sending a message to Glencore chief executive Ivan Glasenberg about the need for a less leveraged balance sheet, they are also sending a message to BHP Billiton and Rio Tinto about their unsustainable dividend policies.
Utilize the input text as a context reference, choose the right relationship between 'Glencore' and 'Ivan Glasenberg' from the options.
Options: distribution format, location of formation, chief executive officer, operator