User blog comment:Simply Beautiful Art/Intuition behind the Mahlo OCF/@comment-36984051-20190831133412/@comment-35470197-20190902131745

But the book was still wrong when I wrote it, especially on OCFs and ordinal notations. Since the author said that he will correct the errors, I recommend you to ask him whether he has completed to fixing the errors.

Also, what he wrote is not Rathjen's OCF, but a variant, which performs in a completely different way.