They were called The Book of Oliver, and they were an illustrated and detailed listing of almost every product that Oliver had for sale at the time. There were three volumes total, with each one an updated version of the previous and all were printed during the 1930s. Discontinued models were removed, so just getting volume 3 won't get you everything.

You can occasionally find them on ebay, but your best bet is a tractor show featuring Oliver. There are vendors that sell literature, and they will occasionally have some for sale. But be ready to spend some $$$, as they routinely fetch  3-4 hundred for ones in good shape, and even more for the leather bound ones.

Here's what the cover of Volume 2 looks like, with the other two looking almost identical except the volume number.