I am looking for a few links to webpages or currently-available books
which answer the below question from a logical or scientific point of
view (preferably credible sources):

What text sizes are easiest to read at certain distances (reading
product packaging, banners, signs) assuming average eyesight?

=OR=

A site to a large scale survey results for what text sizes are used
for headers, fine print, general packaging text, banners, etc.?