2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/107619We prove L^p estimates for a tri-linear operator, whose symbol is given by the product of two standard symbols, satisfying the well known Marcinkiewicz-Hormander-Mihlin condition. Our main result contains in particular the classical Coifman-Meyer theorem. This tri-linear operator is the simplest example of a large class of multi-linear operators, which we called "paraproducts with flag singularities".34 pages, one figureClassical Analysis and ODEs42B25text