Website/Catalog  (1956)  Page(s) [1].  
 
Japanese Tree Peonies
Gekkyuden (Palace of the Moon) Very large full double white...$6.00

Article (magazine)  (Jan 1955)  Page(s) 57.  
 
Alphabetical Check List of Tree Peony Names In  Public Collections And/or Available in Nurseries 1954-1955
Japanese, White, 'Gekkyuden' (Palace of the Moon Kongdom) (Jap. bef. 1910), [Gardens] Scott Foundation

Website/Catalog  (1914)  Page(s) 7.  
 
Paeonia Moutan (Japanese tree peony)
9. Geqqu-den, Large white, 12 [inches across].