[faviouz]

I've been waiting for v4 for a while now. Looks great! I think I'll finally buy it. :)

The PDF preview at https://gumroad.com/l/noBSmath appears to be the old version of the book. You should fix that.

[ivansavz]

The link is actually the same as for v3.0---I just replaced the file with the new one. So if have the gumroad link to the v3.0 file, it should now point to the updated version.