Here's the white-crest incomplete dominant reference:

International Registry of Poultry Genetic Stocks
By RG Somes Jr 1988
https://opencommons.uconn.edu/cgi/viewcontent.cgi?article=1028&context=saes

Quote:
460 WHITE CREST
INHERlT: Autosomal Incomplete dominant
LINKAGE: Unknown
CHARACT: This mutant has nonpigmented white crest feathers, but the rest of the bird's feathers are heavily pigmented being solid black or blue.
REF: Unpublished
SOURCE: White-Crested Black Polish and White-Crested Blue Polish