Why the race link doesn't work?

I am new to FHIR. I was trying to research how race information is stored in FHIR. But the official URL for race doesn’t work. Can someone give me some advice? Thank you very much.

http://hl7.org/fhir/us/core/StructureDefinition/us-core-race

In general, there’s no requirement that extension URLs (or code system URLs - or any canonical URLs) will resolve. In this case, we intend this URL to resolve, but there was a publication issue with the most recent release of US Core that means that (for a little while) the URL doesn’t resolve as we would like it to. That’ll hopefully be fixed in a few weeks. In the meantime, you can certainly go browse the US Core spec to find the extension definition.

Good to know. Thank you so much lloyd!