I think the guy who wrote that original U of C list has stated that it's mainly of historical interest, given the many omissions noted, and that the lists by Baez and Univ. Cambridge that i pushed there are better starting points, or this one: https://www.reddit.com/r/math/wiki/faq

There's lot sof other lists of recommended texts after calc3, https://www.math.ucla.edu/ugrad/courses/math/ and

https://math.berkeley.edu/courses/archives/announcements/fal...

and http://mathoverflow.net/questions/761/undergraduate-level-ma...

Much better. Looking through the intermediate and advanced sections, I see that this guide suffers from none of the omissions which I had complained about in my post (specifically, the omissions of classic works by Arnold and Spivak).

(I still think it would be crazy not to buy the PCtM somewhere before reaching the advanced part of this guide, and it may as well be before the intermediate as well. Consider that without the PCtM, you may never realize that your initial (probably false) assumptions about the scope of mathematics may mean that you will never even get past the beginner section at all!)