BPMN21 — No correct validation rules mentioned

Dear Team

On the provider www.bpmn.io I can create a flow that is exportable to a .BPMN/XML file. In order to check this XML validation the library links to:

<?xml version="1.0" encoding="UTF-8"?>
<bpmn:definitions xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:bpmn="http://www.omg.org/spec/BPMN/20100524/MODEL" xmlns:bpmndi="http://www.omg.org/spec/BPMN/20100524/DI" xmlns:dc="http://www.omg.org/spec/DD/20100524/DC" xmlns:di="http://www.omg.org/spec/DD/20100524/DI" id="Definitions_13r4fun" targetNamespace="http://bpmn.io/schema/bpmn" exporter="bpmn-js (https://demo.bpmn.io)" exporterVersion="8.8.0">

The URLS to Omg.org are giving a page 404.

Question:
Is it possible to support me the correct Omg URLs for the XML header? so the XML can be validated

Kind regards

Dieter Proost