Algebraic and combinatorial codimension-1 transversality
arXiv:math/0308111
Abstract
The Waldhausen construction of Mayer-Vietoris splittings of chain complexes over an injective generalized free product of group rings is extended to a combinatorial construction of Seifert-van Kampen splittings of CW complexes with fundamental group an injective generalized free product.
Published by Geometry and Topology Monographs at http://www.maths.warwick.ac.uk/gt/GTMon7/paper6.abs.html