I'm the Ronni Rosenberg. This was an internal CCA paper (not from academia or a published journal), from 35 years ago! I don't have a copy and I have no idea how to get it. Sorry about that. It does seem to be the earliest reference to data "sharding." (The other early reference mentioned in Wikipedia is from much later, 1997.) Fortunately, you need not go back 35 years to read about sharding; it's easy to get current info. Cheers.