As [MENTION=333224]juvela[/MENTION] mentioned, there's little in the way of official publications you can find online on the DBS as a brand. I think I've only seen one catalog scan and it was from the 90s.
As for the model names, I don't think they changed a lot over the years (at least late 70s to mid 80s) but the specs definitely seem to vary. Here is a list of their models ca 1983, top to bottom:

La Migliore
Professionale
Competition
Internazionale
Nazionale

La Migliore and Professionale were made by Daccordi, Competition by Panasonic and the bottom two were either made by Piazza or someone using Piazza bits (as I've seen them use Piazza dropouts).

Another decent resource for info and pics of DBS bikes is the Terrengsykkel forum.