I saw this online too:
http://www.jlhweb.net/Boxermap/reputablebreeder.html
I have been mulling over the "show aspect" of being a responsible breeder too. I am just not sure about that myself. I would love to find a local Yorkshire Terrier Club but have seen no evidence of one. Nor have I been able to locate any shows close to me -- I would at least like to attend a few. Shows do afford a person an objective evaluation of their dogs for potential breeding, but I can see that it is not for everyone -- maybe not for me either. I will keep looking into this -- I have plenty of time.