Characterizing existence of certain ultrafilters. - Rafal Filipów; Krzysztof Kowitz; Adam Kwela (Ann. Pure Appl. Log., 2022)

"Riesel" and another numbers. - Krzysztof Kowitz; Karolina Miszczyk (Discret. Math. Algorithms Appl., 2024)

Katětov order between Hindman, Ramsey and summable ideals. - Rafal Filipów; Krzysztof Kowitz; Adam Kwela (Arch. Math. Log., 2024)

Generalized "Riesel" numbers and nice numbers. - Krzysztof Kowitz (Discret. Math. Algorithms Appl., 2025)