[hello2023]

In the spacing section, the author's suggestion to use absolute spacing operator (e.g \;) is actually not recommended. a better way is to make `dx` a math operator (`d` is an operator isn't it?).

Some other suggestion is not actually recommended in the official documentation of amsmath as I recall.

Hope this helps.

[hanche]

I use \mathop{}\!{\mathrm d}} myself. That is a bit convoluted, but it takes care of the spacing in just about every context.. Of course, I put that in a macro definition so I don’t have to sprinkle it all over my document.