name the tv show whose network is bbc four and is the subsequent work of ashes to ashes ?
SELECT DISTINCT var_uri where brack_open var_uri dbo_network dbr_BBC_Four sep_dot var_uri dbo_subsequentWork dbr_Ashes_to_Ashes_ attr_open TV_series attr_close sep_dot var_uri a dbo_TelevisionShow brack_close