i'm old, too, but i managed to find this. they are called QR codes. don't ask me what QR means. it's late thirty and i'm tired.
https://www.qrcode-tiger.com/how-to-use-qr-codes-on-flyers-and-brochures
and me? i'm so old i like the feel of a book/things that are tangible.
Ya real books sooooo much better I'm with you on that one for sure.
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