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, Purple, 'Negricans' (Jap. bef. 1864), [Gardens] Scott Foundation

Book  (1907)  Page(s) 157.  
 
1780. NEGRICANS; P. moutan.
(1) 1906, Dessert's Cat., p. 46.