That's odd, American engineers dating *that* far back tend to be fairly forthcoming with information - compared to their corresponding Japanese analogues, at least.
I will say that pretty much no source outside of what's in the patents has escaped Mattel Electronics to my knowledge - everyone there was unusually tight about that stuff. Apparently there's tons of it in Intellivision Productions' warehouse (including their 2600, Coleco, Apple II, and IBM PC ports), but they have Flashback consoles to sell so they aren't giving it out. The ex-programmers are usually willing to chat about technical details at length on the Intellivision podcast (and sometimes they mention the handhelds), but no source.
