{"query": "The check digit that catches a mistyped number", "count": 1, "results": [{"id": "card_works_luhn", "title": "The check digit that catches a mistyped number", "shelf": "the-works", "surface": "secular", "snippet": "The Luhn and ISBN algorithms embed a check digit so a single wrong digit is caught before it becomes a wrong order or a wrong book. Two standards, both verified.  Worked & sealed by the engine — Luhn(", "authority_tier": "verified", "source": "The Works — worked & sealed", "generated": false}]}