I don't have link on that, but the main difficulty with OCR isn't the OCR part (not anymore at least), it's the "clean up" part, and serifs are a pain in the ass, especially on sightly crumpled paper. My use case was an ERP plugin that digitalized and read to receipt to autofill reimbursement demands, and since most receipt use sans-serif fonts, it was mostly fine, but some jokers use serifed font (mostly on receipts you get when using cash, not credit card receipts) and the error rate jumped from like 1% to 13% (not sure about the 1%, it might be a story i told myself to make me feel better, it was a decade ago, before i pivoted to network from AI. I always take the best decision it seems)