1. The integral curves of the equation y'= (ax2+bxy+cy2)/(dx2+exy+fy2) (in Russian);Lyagina;Usp. mat. Nauk,1951
2. Quadratic differential equations and non-associative algebras;Markus,1960
3. The Integral Curves of a Certain Differential Equation;Korol,1973
4. Geometric classification of quadratic differential systems;Sibirskii;Differential Equations,1977
5. Two-dimensional homogeneous quadratic differential systems;Newton;SIAM Review,1978