Or on the arXiv: https://arxiv.org/abs/1811.03792 https://arxiv.org/abs/1811.03792 . It also looks like the first author wrote up a local article which seems

Or on the arXiv: https://arxiv.org/abs/1811.03792 https://arxiv.org/abs/1811.03792 . It also looks like the first author wrote up a local article which seems to have substantially, umm, inspired the linked write up: https://transferencia.tec.mx/en/2019/02/21/eureka-they-find-the-formula-to-solve-an-old-optical-problem https://transferencia.tec.mx/en/2019/02/21/eureka-they-find-... .