\begin{align*}
    &r_{a}^l = \langle \theta^l\; , \; v_{a^l} + w_l v_{{a}^{l-1}} \rangle + \eta^l + \epsilon \Tilde{\eta}^l\\
    &\text{where } \Tilde{\eta}^l \sim \text{Laplace}(0, 1)
\end{align*}
