Maximal linked systems in topology Baayen, Cor P. — 1977 General topology and its relations to modern analysis and algebra IV
On the product and sum of a system of transformation semigroups Cor P. Baayen; Zdeněk Hedrlín — 1963 Commentationes Mathematicae Universitatis Carolinae
Commutative polynomial semigroups on a segment Cor P. Baayen; Zdeněk Hedrlín — 1963 Commentationes Mathematicae Universitatis Carolinae