Morin, Bernard (13 листопада 1978). Équations du retournement de la sphère [Equations of the eversion of the sphere] (PDF). Comptes Rendus de l'Académie des Sciences. Série A (фр.). 287: 879—882.
Goodman, Sue; Marek Kossowski (2009). Immersions of the projective plane with one triple point. Differential Geometry and Its Applications. 27 (4): 527—542. doi:10.1016/j.difgeo.2009.01.011. ISSN0926-2245.
Goodman, Sue; Marek Kossowski (2009). Immersions of the projective plane with one triple point. Differential Geometry and Its Applications. 27 (4): 527—542. doi:10.1016/j.difgeo.2009.01.011. ISSN0926-2245.