Vintage illustration

One of my side passions about kids books is vintage illustration. I've always had a nostalgic fondness for them, but only recently has it turned into a growing hobby.
Today while thrift store rummaging I found a copy of The Joke Book by Oscar Weigle and illustrated by Bill and Bonnie Rutherford. I'm really enjoying the bold craziness of some of these 1950-70's kids books. There's all sorts of silkscreen-like and ink action going on in this one. Here's the cover:

 I was disappointed however, when I tried to find out more about the Rutherfords. I noticed that they had several books to their credit (including Little Black Sambo and The Gingerbread Man) but no biographical information anywhere. This seems a little strange to me. There are other vintage artists out there for which biographical information is readily available. Alice and Martin Provensen, Eloise Wilkin, Richard Scarry, Gustaf Tenggren (Poky Little Puppy), Tibor Gergely (The Little Red Caboose) etc. But no biographical information for the Rutherfords at all.

It makes me wonder what happens to illustrators when no one remembers them? Who is keeping track of all these wonderful vintage artists?

If anyone has more information on the Rutherfords, please let me know!