One of the most-cited "authorities" on serif legibility is Cyril Burt, whose 1955 article [2] in The British Journal of Statistical Psychology (a journal he was

One of the most-cited "authorities" on serif legibility is Cyril Burt, whose 1955 article [2] in The British Journal of Statistical Psychology (a journal he was the editor of) seemed to end the debate on whether serif typefaces are more readable than non-serif typefaces. I think this article is referring specifically to print given the dates of the research.