The tombstone, Halmos, end of proof, or Q.E.D. mark "∎" (or "□") is used in mathematics to denote the end of a proof, in place of the traditional abbreviation "Q.E.D." for the Latin phrase "quod erat demonstrandum", "which was to be shown".
O signo de fin de artigo, tombstone, Halmos, fin da demostración ou signo de Q.E.D. "∎" úsase en Matemáticas para sinalar a fin dunha demostración matemática, en lugar da abreviatura habitual "Q.E.D.", da frase latina "quod erat demonstrandum", "o que se quería demostrar".