...Ward Kimball says so. John Canemaker's beautiful book on the art and lives of Disney's Nine Old Men was first published in 2001. John chronicles the career of these artists thoroughly. There is plenty of art as well as rare photographs. This book is a must have for any animation professional or any Disney fan. I told John once that I feel he wrote this book for me, because I always felt there should be so much more known about them.
Fourteen years later I wrote another volume with my take on the art of these influential artists. Consider it an encore to John's book with a hefty offering of some of their best work.
If you want to complete your Nine Old Men collection, get the Bluray disc of Peter Pan. The bonus material includes Ted Thomas' fantastic documentary Growing up with Nine Old Men. (Outside of the US the documentary was released with The Jungle Book).
Woolie Reitherman working on Mickey and the Beanstalk.
A very young Milt Kahl working on graphic advertisement art a few years before joining Disney Studios.
Here is the link to Amazon: