Shugailo, E. A. “Parallel Affine Immersions ${M^n}\to {{\mathbb{R}}^{n+2 }}$ With Flat Connection”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 65, no. 9, Sept. 2013, pp. 1283–1300, https://umj.imath.kiev.ua/index.php/umj/article/view/2509.