I've been researching copyrights with Google and found a site
http://copyright.cornell.edu/resources/publicdomain.cfm
and I'm confused about what is still copyright protected in the USA. According the cornell site, works first published in the USA in the period 1923 to 1963 with copyright notice but with no renewal are no longer copyrighted. If true, then the 70 year rule in the USA (or the 50 year Canadian rule) does not apply to Levinrew's books because according to the Stanford copyright database, none of his books were renewed.
Am I missing something that should be obvious?
Bob