Maximum independent sets in direct products of cycles or trees with arbitrary graphs. - Tjasa Paj; Simon Spacapan (Discuss. Math. Graph Theory, 2015)

Optimal orientations of strong products of paths. - Tjasa Paj Erker (Art Discret. Appl. Math., 2019)

Separation of Cartesian products of graphs into several connected components by the removal of vertices. - Tjasa Paj Erker; Simon Spacapan (Discuss. Math. Graph Theory, 2022)