On (k, l)-kernels in D-join of digraphs. - Waldemar Szumny; Andrzej Wloch; Iwona Wloch (Discuss. Math. Graph Theory, 2007)

On the existence and on the number of (k, l)-kernels in the lexicographic product of graphs. - Waldemar Szumny; Iwona Wloch; Andrzej Wloch (Discret. Math., 2008)