You can add "negative space" with \!. Try this:
which givesCode:\iiiint\!\!\!\int dx\,dy\,dz\,dt\,du
Also, note the use of the \, spacer. I don't think I have ever seen you use it, but it will make your integrals a bit nicer by putting space between the integrand and the variable of integration. e.g.
Instead of , you'd get .
Actually, I believe he was trying to express a counterclockwise contour integral (look closely and notice the arrow).
I found this really old post on comp.text.tex by Donald Arseneau that provides a method to get it to look right, but I do not think these forums have the right packages.
Note the part in red. The intention was for a counterclockwise line integral...Code:\mathop{\int\mkern-20.8mu \circlearrowleft}\nolimits_C {{\mathbf{F}} \cdot d{\mathbf{r}}} = \iint\limits_R {{\text{curl}} \,{\mathbf{F}} \cdot {\mathbf{k}}\,dA}
You probably don't see the arrow because the arrow is at the top of the circle:
...The integral sign blocks it...