A ${\mathbb {Z}}_{2}{\mathbb {Z}}_{4}$ -additive code ${\mathcal{ C}}\subseteq {\mathbb {Z}}_{2}^\alpha imes {\mathbb {Z}}_{4}^\beta $ is called cyclic if the set of coordinates can be partitioned into two subsets, the set of ${\mathbb {Z}}_{2}$ and the set...