Gheorghiu, Călin Ioan, and Damian Trif. “Direct and Indirect Approximations to Positive Solution for a Nonlinear Reaction-Diffusion Problem. II. Indirect Approximation”. Rev. Anal. Numér. Théor. Approx., vol. 31, no. 2, Aug. 2002, pp. 163-70, https://doi.org/10.33993/jnaat312-720.