Re:These works were written between 40 - 60 years (Score 1)

Yes, in Life+70 countries that can easily happen. In the US, anything published before 1923 is in the public domain. Anything from 1923 onward requires a lot of research, which sometimes leads to mistakes (as in the Rule 6 clearance referenced above, "The Escape", aka "Brainwave"). Actually, it's not so much a mistake as an oddity in the law. The first publication, as a serial, was not renewed. Only the later republication as "Brainwave" was renewed.