which is unsubstituted or substituted by halogen atoms or alkyl or alkoxy groups having 1-4 C atoms, or a phenoxy group or a group of the formula --NHQ, in which Q is a hydrogen atom, an alkyl group containing 1-6 C atoms or a phenyl radical which is unsubstituted or substituted by halogen atoms or alkyl or alkoxy groups having 1-4 C atoms.