Some works from other nations than America

Hey there guys, just looking for some advice on whether any of the people that are mentioned in this list are actually available for public domain use? How would this differ if I was in the US, the nation of character's origin, or elsewhere in the Commonwealth? I'm predominantly interested in these ones (the links have their first publication dates and the like):

Atom-Man
Captain Might
Captain Wonder
Captain Zenith
Fantax
Powerman
Thunderfist

Australia's copyright expiration laws seem a bit murky:

an official AU copyright site wrote:

Copyright in a published written work has expired if it:

was published before 1955 AND the author died before 1955, or

was published anonymously or under a pseudonym before 1955 AND the identity of the author cannot be ascertained on reasonable inquiry, or

was made for, or first published by, a government (Commonwealth, State or Territory), and published before 1959.
A work is ‘published’ in this context if copies have been distributed, or it has been publicly performed or broadcast.

Canada has the "50 years after author's death" length for copyright. Britain shares roughly the same law as Australia.
For Fantax, I have no idea.

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All Glory and Honor and Praise be to God The Father, God The Son, and God The Holy Spirit, Amen.

Hrm, how frustrating. I can't seem to find any records online for several of these publications or publishing companies, so I'm unable to determine the authors. That impedes my research somewhat, may have to try to find out if there are any hard copy records for these comics by any organisations or archives that I can contact, but no idea where to start looking for them.

Thanks for the advice anyway, Yzz. At least that sort of helps clarify it, wasn't sure if there were ever times that registrations were needed in those countries, seems not.