A Quick proof of Singhof's cat (M x S1) = cat (M) + 1 theorem. Luis Montejano — 1983 Manuscripta mathematica
About a problem of Ulam concerning flat sections of manifolds. Luis Montejano — 1990 Commentarii mathematici Helvetici
Lusternik-Schnirelmann category and minimal coverings with contractible sets. Mónica Clapp; Luis Montejano — 1987 Manuscripta mathematica