P: 116 Hello, I am reading the paper "Covariant Action for a D=11 Five-Brane with the Chiral Field". I don't understand the $(\partial a)^2$ in the dual field strength $\widetilde{F}_{mn}\equiv\frac{1}{\sqrt {(\partial a)^2}}F^*_{mnl}\partial^la(x)$. Is it ##\partial_ra\partial^ra##? Regards.