name the military unit whose garrison is polykastro and command structure is hellenic army ii mechanized infantry division ?
SELECT DISTINCT var_uri where brack_open var_uri dbo_garrison dbr_Polykastro sep_dot var_uri dbo_commandStructure dbr_Hellenic_Army_II_Mechanized_Infantry_Division sep_dot var_uri a dbo_MilitaryUnit brack_close