Just a quick question, I am going through some books on complex analysis and I'm wondering what an integral like $\int_f f(z,\bar{z}) \sqrt{dz d\bar{z}}$ means. How is one supposed to take that notation to mean something?? I have not come across things that have roots over the dz's and d\bar{z}'s. Besides, the integral here is a single integral, but there are two variables involved?
I am assuming I can do that as perhaps I can parametrise $f$ in terms of some parameter $t$.
Thanks