The $k$-metric dimension of corona product graphs
  Given a connected simple graph $G=(V,E)$, and a positive integer $k$, a set $S\subseteq V$ is said to be a $k$-metric generator for $G$ if and only if for any pair of different vertices $u,v\in V$, there exist at least $k$ vertices $w_1,w_2,...,w_k\in S$ such that $d_G(u,w_i)\ne d_G(v,w_i)$, for every $i\in \{1,...,k\}$, where $d_G(x,y)$ is the length of a shortest path between $x$ and $y$. A $k$-metric generator of minimum cardinality in $G$ is called a $k$-metric basis and its cardinality, the $k$-metric dimension of $G$. In this article we study the $k$-metric dimension of corona product graphs $G\odot\mathcal{H}$, where $G$ is a graph of order $n$ and $\mathcal{H}$ is a family of $n$ non-trivial graphs. Specifically, we give some necessary and sufficient conditions for the existence of a $k$-metric basis in a connected corona graph. Moreover, we obtain tight bounds and closed formulae for the $k$-metric dimension of connected corona graphs. 
Alejandro Estrada-Moreno, Ismael Gonzalez Yero and Juan Alberto   Rodriguez-Velazquez
math.CO