From:
http://eastlandkennels.com/history_o...wer_yorkie.htm
The Biewer Yorkie was originally a piebald genetic recessive gene occurrence from 2 Yorkshire Terriers but unscrupulous breeders have tried to match the look 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 very 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.