Finally, note that the winding number is closely related with the (2 + 1)-dimensional continuous Heisenberg ferromagnet equations and its integrable extensions: the Ishimori equation etc.
Schrödinger equation | Nernst equation | Monge–Ampère equation | Boltzmann equation | Diophantine equation | Ordinary differential equation | ordinary differential equation | Young–Laplace equation | Wave equation | wave equation | Vlasov equation | Tait equation | Smoluchowski coagulation equation | Sauerbrey equation | Redlich–Kwong equation of state | Ramanujan–Nagell equation | Quadratic equation | Prony equation | Pell's equation | Mathieu's equation | Marchenko equation | Majorana's equation | Linear equation | linear equation | Liénard equation | Kepler's equation | Kaup–Kupershmidt equation | Ishimori equation | Hyperbolic partial differential equation | Heun's equation |