Add to ORKGThe interaction Hamiltonian within the Bloch gauge for the potentials of the electromagnetic field has been usedto define electromagnetic multipole moment operators and operators for the magnetic field of electrons acting onthe nuclei of a molecule. Perturbation theory has been applied to evaluate the induced electronic moments andmagnetic field at the nuclei. Multipole magnetic susceptibility and nuclear magnetic shielding tensors have beendefined to describe the contributions arising in non-uniform magnetic fields, and their origin dependence has beenanalyzed. Extended numerical tests on the water molecule in a static, non-unifo~ magnetjc field have been carriedout, using the random-phase approximation within the framework of accurate Har...