David Cohen-Steiner Herbert Edelsbrunner John Harer Extending Persistence Using Poincaré and Lefschetz Duality. 133-134 2009 9 Foundations of Computational Mathematics 1 http://dx.doi.org/10.1007/s10208-008-9038-9 db/journals/focm/focm9.html#Cohen-SteinerEH09a