With no explanation, label text_A→text_B with either "not_related" or "related".
text_A: Nas was ranked number seven on The Source's list of the "Top 50 Lyricists of All Time".
text_B: `` For Richer For Poorer '' is an episode of the BBC Sit-com , The Green Green Grass .. BBC. BBC. Sit-com. Sit-com. The Green Green Grass. The Green Green Grass. It was screened on 5 March 2009 , as the last episode of the fourth series and the last episode of the entire programme .
not_related.