Gilad M. Lerman and Levy, Uriel . 7/24/2007. “Tight Focusing Of Spatially Variant Vector Optical Fields With Elliptical Symmetry Of Linear Polarization”. Optics Letters, 32, 15, Pp. 2194-2196. https://www.osapublishing.org/ol/abstract.cfm?uri=ol-32-15-2194.