That's a superb overview and a must-bookmark item.
There are a couple of legal subtleties that researchers (and would-be republishers) of old works need to be aware of. The most important of these is that there are requirements for a valid copyright notice. As I understand it (and I'm a publisher, not a lawyer) a copyright notice for printed works must have these three elements to qualify under the law:
- The copyright symbol, the word "copyright" or the abbreviation "copr."
- The year that the printed item was first published
- The name of the person or organization claiming copyright on the printed work
Note that this is the case for printed works; requirements are looser for graphics, photographs, or sculptures, but I don't work in those fields and haven't studied them. For printed works, if any one or more of these items is missing, the copyright notice is not valid and thus not binding.
The most common failing of a copyright notice is lack of a year. "Copyright by John Q. Clueless" is
not a valid notice. I have only once or twice seen an item with a notice like "Copyright 1937" but that is not sufficient under the law. I don't know whether abbreviations
other than "copr." qualify, but I wouldn't choose to get in a row with Time Warner over it.
Again, all the usual IANAL cautions apply here, but this is the law as I understand it.