As a concrete example, I've come across several papers who cite Claude Shannon's entry on Information Theory, from Encyclopaedia Britannica vol. 12, p. 246b, and recommend it as a good starting point in the field.

It's available at https://archive.org/details/encyclopdiabrita12chic/page/n307... .

I think it's a better intro than the Wikipedia one for someone looking for an intro overview.

The Wikipedia has a bunch more cross-references and goes into more depth.