1. Invariants of the Lusternik–Schnirelmann type and the topology of critical sets;Clapp;Trans. Amer. Math. Soc.,1986
2. Topology;Dugundji,1967
3. Lusternik–Schnirelmann category of 3-manifolds;Gómez-Larrañaga;Topology,1992
4. 3-manifolds that are covered by two open Bundles;Gómez-Larrañaga;Bol. Soc. Mat. Mexicana (3),2004
5. J.C. Gómez-Larrañaga, F. González-Acuña, W.H. Heil, 3-manifolds with S1-category 2, in preparation