2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/35531The usual composition rule of independent systems, as applied to decoherent histories or to linearly positive histories, requires (at least) medium decoherence and, consequently, a second constraint for the linearly positive histories of Goldstein and Page. Other plausible classical features, valid for medium decoherence, seem anyhow to be missed by linear positive histories.5 pages LaTeXGeneral Relativity and Quantum Cosmologytext