Book  (Jan 2000)  Page(s) 226, 231.  
 
Page 226: Flight of Cranes. See 'Renkaku'.
Page 231: Renkaku Tree Peony. ex Japan 1931. Also sold as 'Flight of Cranes'... white

Book  (1999)  Page(s) 138.  
 
Paeonia suffruticosa 'Renkaku', cv., 1972

Article (magazine)  (Jan 1955)  Page(s) 20.  
 
In white, (Class I, of the American Peony Society), there are 'Gessekai,' 'Godaishu,' 'Fugi-oe-ryo,' 'Renkaku,' and 'Yaso-okina,' which are pure white throughout, 'Ima-chowkow,' which is creamy, and 'Kogane-zome' and 'Shuchiuka,' with pinkish and purplish splashes.

Article (magazine)  (Jan 1955)  Page(s) 59.  
 
Alphabetical Check List of Tree Peony Names In  Public Collections And/or Available in Nurseries 1954-1955
Japanese, White, 'Renkaku' (Flock of Cranes, or Flight of Cranes) (Jap. bef. 1931), [Gardens] Morton Arboretum, Scott Foundation, Whitnal Park Botanical Gardens, [Nurseries] Oberlin Peony Gardens

Website/Catalog  (1939)  Page(s) [1].  
 
Tree Peonies (Pæonia arborea)
Japanese Tree Peonies 
English translation in parentheses
52. Rein-Kahu (Flight of Cranes). Large; double; fragrant; pure white, with central cushion of golden anthers. Profuse bloomer... $5.00

Website/Catalog  (1924)  Page(s) 152.  
 
Pivoines en arbre, du Japon...Renkaku.- Blanc semi-double.

Website/Catalog  (1914)  Page(s) 8.  
 
Paeonia Moutan (Japanese tree peony)
20. Ren-kaku, White large flower, 12 [inches across].

Website/Catalog  (1909)  Page(s) 11.  
 
Paeonia Moutan...
14. Renkaku, white large flower, 12 inches

Website/Catalog  (1898)  Page(s) 11.  
 
PÆONIA MOUTAN. (Tree Peonies.)
14. Renkaku, white large flower.