Many of our useful references are long out of protection by copyright - and so have been republished and ebooked and generally propagated into the mass market. That is both to our benefit as regards beginner students and our detriment as the number of novel practical methods that come into use in a decade is far less than the number of such methods which are set into print and described in detail by way of these older books - never mind the base semi-exposure of indiscriminate use of online resources including YouTube.
However, should such a book be annotated and include additional content - this new work would fall under copyright protection. Consider the utility of Expert Card Technique that is properly credited and contains sufficient historical data and technical demonstrations to permit today's students to learn the material as it was in use at the time of the works original writing. This would serve our historical record and permit those who are specialists in the matter of historical attributions to get their work recognized and those who have taken the trouble to fill in the missing (or incorrect) explanatory data to get their kudos as well.
What such a practice of regular update would provide is both works protected by copyright and kept relatively up to date as regards matters of historical provenance and context.
For the record, this came to me in considering that under ISO each document has an author and review date and the company has a procedure for the regular review of documents and keeps records of that process.
What do you think?