Ojeda Castaneda, Jorge, and Cristina Margarita Gómez-Sarabia. “Nonconventional Optical Systems Using Varifocal Lenses”. Photonics Letters of Poland, vol. 7, no. 1, Apr. 2015, pp. pp. 14-16, doi:10.4302/photon. lett. pl.v7i1.559.