The [Service Discovery](https://xmpp.org/extensions/xep-0004.html#disco) section of XEP-0004 contains a dead link to <https://xmpp.org/extensions/xep-0004.html#ns> (Protocol Namespaces). Shouldn't it link to <https://xmpp.org/extensions/xep-0004.html#registrar-namespaces> instead? The same issue happens for XEP-0016 and other XEPs that use the `NSNOTE` entity without having a section with the attribute `anchor='ns'`.