This article is written years after the 16-bit problem was solved, yet seems to be completely unaware of the solution. (It's unclear if the mentions of adding "octet blocks" is a misunderstanding of the solution, or a dismissal.) It mentions Unicode 3.1, yet surrogate pairs were introduced in Unicode 2.0 five years before the doc was written.

In actuality we don't concern ourselves overmuch with planes, "octet blocks", and so on these days. There's just a single numbered list of characters* that we call "Unicode", and a few fairly minimal algorithms for transforming a list of characters into a bytestream ("UTF-8", "UTF-16", etc).

Still I love it as a historically interesting document. It's jarring to see "Oriental" used, I suspect the same author would never use that word in a professional context today.

[*] I use "characters" here when "code points" would be more accurate, but the details of that comparison aren't meaningful to this argument. I also don't go into normalization and so on, as this article seems to be more about the feasibility of fitting >100K code points into actual-bits-on-the-wire.