“…However, these methods do not succeed in reconstructing the stress components separately and therefore the full stress tensor, and the linearly related dielectric tensor, can be obtained in this way only for systems exhibiting a certain degree of symmetry, such as an axial symmetry. Other methods of reconstruction have been suggested, for example, a three-beam measurement scheme [22], where for axisymmetric systems an onion-peeling reconstruction algorithm was proposed [23,24]. Another method, which in principle is capable of determining a general three-dimensional permittivity tensor, is the "load incremental approach" [25].…”