There are (I think) 3 different Biewer clubs in America. Here's the links for them. You will see that 2 state that the Biewer is a separate breed from the Yorkshire, while one uses the term 'Biewer Yorkies".
Biewer Terrier Club of America, Inc. Biewer Breed Club of America index
One curious thing. I see Biewers in the
Yorkshire Terrier Nursery forum and also the
Yorkshire Terrier For Sale forum. If they're a separate breed, shouldn't they be in the "Our Yorkies Brothers and Sisters" forum? Just asking...