Constraint on linear, homogeneous, constitutive relations

Abstract
A constraint on linear, homogeneous, constitutive relations is presented. It does not affect the sources and the primitive fields, its effect being solely on the induction fields. As the Maxwell postulates are satisfied without question, its use amounts to a simplification of the description of linear, homogeneous, magnetoelectric media. The constraint is in complete harmony with the covariant character of modern electromagnetic theory.