Book  (1990)  Page(s) 91.  Includes photo(s).
 
Bischof Dr Korum
Hybrid Perpetual (1922)
... an unusual member... in that it has some yellow in it... very fragrant... coloured lemon with light pink...

Article (magazine)  (Dec 1951)  Page(s) 207.  
 
Bischof Dr. Korum Hybrid Perpetual. Lambert 1921. Description... yellow with pink shading, aging silver pink...

Book  (1940)  Page(s) 21.  
 
Biscof Dr. Korum Hybrid Perpetual. (P. Lambert, 1921)... yellowish rose, with silvery shade.

Book  (1936)  Page(s) 390.  
 
Korum, Bischof Dr. (HP) Lambert 1921; Druschki X L. Carle; silky yellowish to centifolia-pink, edges silvery, very large, double, cup form, fine form, lasting, solitary, fragrance 7/10, floriferous, continuous bloom, strong stems, many prickles, light green foliage, growth 6/10, growth 6/10, upright, bushy. Sangerhausen