Keywords you may use for searching:
Experts - historian; scientist; archaeologist,
Opinion - theory, theories
The theory may be in an article, for example National Geographic or Archaeology
or
on a .edu or .org or .gov site
and will mention someone's name as the expert.
You can google their name to find out their credentials
Example : you may google the bog body or ancient remains you are researching and add some of the above keywords