Book  (Oct 2001)  Page(s) 132-133.  Includes photo(s).
 
Clematis 'Blue Boy'
Herbaceous/Integrifolia Group
Frank L. Skinner (Canada) 1947
C. integrifolia x C. viticella
... bell-shaped, nodding, hyacinth-blue to midblue flowers... four tepals... white filaments and yellow anthers...