^ Macan, Edward (November 24, 1997). “Rocking the Classics: English Progressive Rock and the Counterculture”. Oxford University Press. November 24, 2017閲覧。
https://books.google.com/books?id=2jtQAElFVUcC Holm-Hudson, Kevin, ed (2013). Progressive Rock Reconsidered. Routledge. ISBN 978-1-135-71022-4. https://books.google