Book  (Oct 2001)  Page(s) 134-135.  Includes photo(s).
 
Clematis 'Boskoop Beauty'
J. de Vink (Netherlands) ca. 1960
Open-pollinated seedling of C. 'Nelly Moser'
... Not very floriferous... single, large, pale lilac flowers... six or seven tepals... lilac-purple stripe runs along the centre [of each tepal]. Creamy filaments with dark red anthers and prominent white styles...

Book  (Apr 1998)  Page(s) 127.