buildingsmart sources not found
http://www.buildingsmart-tech.org/ifc/IFC4/Add1/html/ gives a 404 error.
I suppose that all the occurrences need to be replaced by https://standards.buildingsmart.org/IFC/RELEASE/IFC4_1/FINAL/HTML/
WARNING! Gitlab maintenance operation scheduled for Monday, 20 April between 12:00 and 14:00 (CET). During this time window, short service interruptions (less than 5 minutes) may occur. Thank you in advance for your understanding.
http://www.buildingsmart-tech.org/ifc/IFC4/Add1/html/ gives a 404 error.
I suppose that all the occurrences need to be replaced by https://standards.buildingsmart.org/IFC/RELEASE/IFC4_1/FINAL/HTML/