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The Biewer was originally a banded/belted genetic recessive gene occurrence from 2 Yorkshire Terriers but unscrupulous breeders have tried to match the looks of the Biewer Yorkshire by crossing the Yorkshire Terrier and the Shih-Tzu. The crossing will produce the parti/piebald white markings from the Shih-Tzu influence after the second generation but these crossbred dogs would take generations before they would produce the hair coat and the facial features seen in the Biewer Yorkshire. If the dog being presented to you as a Biewer Yorkshire has wavy and/or course hair, or the facial features or body style of the Shih-Tzu then it's highly unlikely that it is a TRUE purebred Biewer Yorkie.
also googled.
here is the source:
BIEWER YORKIE History