Let usconsider the vector space. Its projectivization, is a projective space, which is obtained from , by factorization relative to the collinearity of vectors. The projectivization is a set of straight lines, passing through the point . Under projectivization, the cone becomes a manifold of dimension .
1997, M. E. Alferieff (translator), Alexei Kostrikin, Yuri Manin, Linear Algebra and Geometry, Gordon and Breach Science Publishers, Paperback, page 233,
Therefore, the projectivization is determined only on the complement .
2004, Alexey Glutsyuk, Confluence of singular points and Stokes phenomena, Yulij Ilyashenko, Christiane Rousseau, Gert Sabidussi (editors), Normal Forms, Bifurcations and Finiteness Problems in Differential Equations, Kluwer Academic, page 290,