They first introduce dual variables
$u_{hi}$, $v_{h}$, $\lambda_{i}$, and $w_l$ for any
$h \in V$, $ i \in N$, and $l \in L$.
They first introduce dual variables
$u_{hi}$, $v_{h}$, $\lambda_{i}$, and $w_l$ for any
$h \in V$, $ i \in N$, and $l \in L$.