Thank you for alerting us to it, we very much appreciate you taking the time.
It turns out only the leading underscore character (before '04') was superfluous; it should have been removed during the last renaming of our files. The links are to sub-directories on Github, since we provide both the ipynb files, as well as rendered html versions of the notebooks.
Please don't hesitate to let us know if we can do anything else.
Robert for the Data Lab team