Utilize the input text as a context reference, choose the right relationship between Syriza and Athens 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.

Nobel prize winning economist Paul Krugman, a vocal supporter of Athens in its long-running bailout saga, said Sunday that he "may have overestimated the competence of the Greek government," suggesting Syriza staged the showdown without having a Plan B.

Answer: headquarters_location