Duca, Dorel I. “Necessary Optimality Criteria in Nonlinear Programming in Complex Space With Differentiability”.
Anal. Numér. Théor. Approx.
, vol. 9, no. 2, Aug. 1980, pp. 163-79,
https://ictp.acad.ro/jnaat/journal/article/view/1980-vol9-no2-art2
.