?Equity markets largely in the red... coming down off yesterday's heady reaction to news of a Greek deal, as Alexis Tsipras returns to a revolution within his Syriza party," said Augustin Eden, research analyst at trading firm Accendo Markets.
In the context of the input sentence, determine the relationship between 'Syriza' and 'Alexis Tsipras'.
Options: subsidiary, owner of, chairperson, chief executive officer