Citation Hunt

The Wikipedia snippet below is not backed by a reliable source. Can you find one?

Click I got this! to go to Wikipedia and fix the snippet, or Next! to see another one. Good luck!

In page Else Marie Pade:

This text has been unreferenced on Wikipedia for a very long time. If you can't find a source, be bold and remove it!

"

This was composed after visit to the planetarium at Expo 58 in Brussels. The composition shows the night sky with the stars and their movement relative to each other. The work is based on Ligeti's principles of sound colours, Boulez's serialism and Stockhausen's mathematically organized score.[citation needed]