Congress knows full well the definition of NBC. They have tried unsuccessfully to change it for the last 19 years which proves their knowledge and intent to subvert the constitution, led by Lawrence Tribe. This link has a lot of information on the various attempts which should make it easier to research on whose behalf they were made. There is also a link to a more extensive discussion at that site.
Congressional Natural Born Citizen Parts I, II & III: Who Knew What & For How Long?
Oh no - link says this;
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It looks like nothing was found at this location. Maybe try a search?