Goodman, G. S., and J. A. Yorke. “Misbehaviour of Solutions of the Differential Equation $y’=f(x,y)+\varepsilon$ When the Right Hand Side Is Discontinuous”. MATHEMATICA SCANDINAVICA 27 (June 1, 1970): 72–76. Accessed August 13, 2026. https://tidsskrift.dk/math/article/view/10988.