Jacques Vélu worked on elliptic curves and explicit isogenies. The original Bordeaux seminar archive verifies the name and his 1970–1971 contribution on elliptic curves.[ref]
https://www.numdam.org/item/STNB_1970-1971____A20_0/. Original seminar author record
Vélu's formulas construct an isogeny from an elliptic curve and a finite kernel subgroup by summing coordinate corrections over the nonidentity kernel points. They turn the abstract quotient by a subgroup into explicit equations for both the map and the quotient curve. The simple short-Weierstrass formulas require characteristic restrictions and do not replace the distinction between geometric kernel points and inseparable degree.[ref]
Isogeny kernels and division polynomials by Andrew Sutherland. Lecture 5, Theorems 5.11, 5.13 and 5.15, explicit Vélu formulas and hypotheses
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