2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/190711We identify type IIA orientifolds that are dual to M-theory compactifications on manifolds with G_2-holonomy. We then discuss the construction of crosscap states in Gepner models. (Based on a talk presented by S.G. at PASCOS 2003 held at the Tata Institute of Fundamental Research, Mumbai during Jan. 3-8, 2003.)3 pages, RevTeX, PASCOS '03 talkHigh Energy Physics - Theorytext