## ABSTRACT

We recall from Sec. 3.4 that the set of free Maxwell equations in the framework of Special Relativity can be written in manifest covariant form as follows:

∂αF αβ = 0, (8.1)

∂αFβγ + ∂βFγα + ∂γFαβ = 0, (8.2)

where Fαβ and Fαβ are the field tensor written in contravariant [Eq. (3.53)] and covariant [Eq. (3.61)] form, respectively. For brevity, we have omitted the subscript T on the field tensor; compare Eqs. (3.58) and (8.1).