Palacios, Julian (2010). Syd Barrett & Pink Floyd: Dark globe. London: Plexus. s. 265. ISBN978-0-85965-431-9. «Waters borrows a succinct line from 9th-century poet Li He's 'Don't Go Out of the Door', which appeared in the original poem as: 'Witness the man who raved at the wall as he wrote his questions to Heaven.'»