2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/131418Recently, Rips produced an example of a double of two free groups which has unsolvable generalized word problem. In this paper, we show that Rips's example fits into a large class of doubles of groups, each member of which contains F_2 x F_2 and therefore has unsolvable generalized word problem and is incoherent.5 pages, 1 figureGroup TheoryGeometric Topology20Exxtext