What great questions and information!
Joan Gordon is a good source of information. Her last known address was
1651 West Ridgewood, Glennview, IL 60025. I know that she loves to share her knowledge and experience with Yorkies lovers. I don't have a phone number or email for her. At her age she may not email. Feel free to write her.
I just looked and there is a letter from Joan Gordon posted on a website:
Joan Gordon - Quality Traditional and Parti Yorkshire Terriers
It was difficult to read the address but it appears to be the same as listed above.