Utilize the input text as a context reference, choose the right relationship between Stathis Kalyvas and Yale University 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.

Yale University political science professor Stathis Kalyvas said the Greek government will face daunting challenges no matter which way the vote goes.

Answer: employer