I've been told that the YTCA page is not all inclusive, it more of a summery, and its says. “A Blueprint or Guide (Illustrated Discussion) as to what the Parent  Club considers to be the correct Yorkshire Terrier can be obtained by  contacting the club secretary.   
owen@kvnet.org” 
Yorkshire Terrier Club of America Official Breed Standard   I wonder if it describes temperment more in the Illustrated Discussion?