I am trying to find the likelihood estimator for the vector of coefficients $\delta$ ($\delta$ is a column vector of size $(p \times 1)$). For that, I have to solve the following score equation
$$\sum_{i}^{n}\sum_{j}^{m_i}\left[ V_{ij}^T-r_{ij}\exp\left\lbrace V_{ij}\delta\right\rbrace V_{ij}^T \right]=0$$
$V_{ij}$ is a row vector of size $(1 \times p)$; $r_{ij}$ is a positive number.
How do I solve such an equation to find $\delta$?