Azarbaijan Shahid Madani University Communications in Combinatorics and Optimization 2538-2128 4 1 2019 06 01 The Italian domatic number of a digraph 61 70 13845 10.22049/cco.2019.26360.1102 EN Lutz Volkmann RWTH Aachen University Journal Article 2018 10 26 An Italian dominating function on a digraph $D$ with vertex set $V(D)$ is defined as a function $f\colon V(D)\to \{0, 1, 2\}$ such that every vertex $v\in V(D)$ with $f(v)=0$ has at least two in-neighbors assigned 1 under $f$ or one in-neighbor $w$ with $f(w)=2$. A set $\{f_1,f_2,\ldots,f_d\}$ of distinct Italian dominating functions on $D$ with the property that $\sum_{i=1}^d f_i(v)\le 2$ for each $v\in V(D)$, is called an  Italian dominating family (of functions) on $D$. The maximum number of functions in an Italian dominating family on $D$ is the  Italian domatic number of $D$, denoted by $d_{I}(D)$. In this paper we initiate the study of the Italian domatic number in digraphs, and we present some sharp bounds for $d_{I}(D)$. In addition, we determine the Italian domatic number of some digraphs. https://comb-opt.azaruniv.ac.ir/article_13845_b207051edc37d9a82ecd605da8ed79b4.pdf