Ţigan, Ştefan. “Linearization Procedure and Kortanek-Evans Optimality Conditions for Symmetric Pseudo-Concave Programming”. Rev. Anal. Numér. Théor. Approx., vol. 22, no. 1, Feb. 1993, pp. 113-20, https://ictp.acad.ro/jnaat/journal/article/view/1993-vol22-no1-art12.