where are all the episodes of crisis on earth x?
['Supergirl, Season 3 Episode 8 (aired on Monday night, 8/7c)', 'Arrow, Season 6 Episode 8 (aired on Monday night, 9/8c)', 'The Flash, Season 4 Episode 8 (airing on Tuesday night, 8/7c)', 'Legends of Tomorrow, Season 3 Episode 8 (airing on Tuesday night, 9/8c)']