The laws and objects in classical electromagnetism can be written in a form which is "manifestly covariant" in vacuum (or for the microscopic Maxwell equations, not using macroscopic descriptions of materials such as electric permittivity).
The laws and objects in classical electromagnetism can be written in a form "manifestly covariant" in vacuum (or for the microscopic Maxwell equations, not using macroscopic descriptions of materials such as electric permittivity). This form is.