{
    "$schema": "http://json-schema.org/draft-04/schema#",
    "additionalProperties": true,
    "definitions": {},
    "properties": {
        "sample_date": {
            "_format": "date",
            "description": "Date on which this fact was known to be true",
            "type": "string"
        },
        "source_url": {
            "description": "Place where this fact can be verified",
            "type": "string"
        }
    },
    "required": [
        "source_url",
        "sample_date"
    ],
    "type": "object"
}