Article (magazine)  (Jan 1955)  Page(s) 56.  
 
Alphabetical Check List of Tree Peony Names In  Public Collections And/or Available in Nurseries 1954-1955
Japnese, Pink, 'Beikoku' (America), (Jap. bef. 1890), [Gardens] Morton Arboretum, Whitnal Park Botanical Garden, [Nurseries] Oberlin Peony Garden

Website/Catalog  (1941)  Page(s) [3].  
 
Tree Peonies
Beikoku (America). Large; semi-double; beautiful soft flesh-pink. Very profuse on upright stems...$5 00

Website/Catalog  (1939)  Page(s) [1].  
 
Tree Peonies (Pæonia arborea)
Japanese Tree Peonies 
English translation in parentheses
30. Beikoku (America). Large; semi-double; beautiful soft flesh-pink. Blooms very profusely on upright stems... $5.00