When you open a candidate PDF, skip to the section on "index ellipsoid" or "dielectric tensor" – if those are explained with clear mathematics and diagrams, it is a legitimate crystal optics resource.
© Philip Plisson / Pêcheur d'ImagesWhen you open a candidate PDF, skip to the section on "index ellipsoid" or "dielectric tensor" – if those are explained with clear mathematics and diagrams, it is a legitimate crystal optics resource.