Book  (Oct 2001)  Page(s) 123.  Includes photo(s).
 
Clematis 'Barbara Jackman'
Rowland Jackman of George Jackman and Son, England, 1947
Named for his wife
Introduced 1952
Rowland Jackman's propagator, A. Voneshon, thought it might have been a seedling of C. patens
... single, bluish mauve flowers... eight broadly overlapping tepals, tapering towards the tips, each with a crimson central bar... creamy stamens...

Book  (1999)  Page(s) 234.  
 
...purple-blue with a magenta bar but fading to a paler mauve-blue

Book  (11 Nov 1996)  Page(s) 37.