2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/102318Let D be a domain in the quaternionic space H. We prove a differential criterion that characterizes Fueter-regular quaternionic functions f:bD -> H of class C^1. We find differential operators T and N, with complex coefficients, such that a function f is regular on D if and only if (N-jT)f=0 on the boundary of D (j a basic quaternion) and f is harmonic on D. As a consequence, by means of the identification of H with C^2, we obtain a non-tangential holomorphicity condition which generalizes a result of Aronov and Kytmanov. We also show how the differential criterion and regularity are related to the dibar-Neumann problem in C^2.13 pages; added references; small changes. To appear on Complex Variables and Elliptic EquationsComplex Variables32A30text