Types

Linear approximated space-time

Curved space-time

Homogeneous

${\partial }_k{F}_{li}+{\partial }_i{F}_{kl}+{\partial }_l{F}_{ik}=0$

${\nabla }_k{F}_{li}+{\nabla }_i{F}_{kl}+{\nabla }_l{F}_{ik}=0$

Inhomogeneous

$J^i={\partial }_j{F}^{ij}$

$J^i={\nabla }_j{F}^{ij}$