Thanks for the comments about links of related interest, for example links about studying advanced mathematics. One comment here suggested that the original author's selection criteria of free and online[1] have allowed in some links that are not really very good.
With that idea in mind, it occurs to me that we could help Gerard t'Hooft, Nobel laureate in physics and the author of the site submitted here, by sending him the best links that his site doesn't already have that would help people learn more background for physics and physics proper. He surely hasn't been able to find all the best links by himself.
[1] "It is my intention to search on the web where the really useful papers and books are, preferably downloadable as well. This way, the costs of becoming a theoretical physicist should not exceed much the price of a computer with internet connection, a printer, and lots of paper and pens."
With that idea in mind, it occurs to me that we could help Gerard t'Hooft, Nobel laureate in physics and the author of the site submitted here, by sending him the best links that his site doesn't already have that would help people learn more background for physics and physics proper. He surely hasn't been able to find all the best links by himself.
[1] "It is my intention to search on the web where the really useful papers and books are, preferably downloadable as well. This way, the costs of becoming a theoretical physicist should not exceed much the price of a computer with internet connection, a printer, and lots of paper and pens."