Disjoint Homotopic Paths and Trees in a Planar Graph. A. Schrijver — 1991 Discrete & computational geometry
The dependence of some logical axioms on disjoint transversals and linked systems A. Schrijver — 1978 Colloquium Mathematicae
Characterizations of supercompact spaces Schrijver, A. — 1977 General topology and its relations to modern analysis and algebra IV