GUPTA V, Gancho TACHEV GT. A modified Post Widder operators preserving eᴬˣ. Stud. Univ. Babeş-Bolyai Math. [Internet]. 2022 Oct. 24 [cited 2025 Feb. 5];67(3):599–606. Available from: https://studia.reviste.ubbcluj.ro/index.php/subbmathematica/article/view/1555