Let $P = (\Omega, \mathcal{F}, \mathbb{P})$ be a D1159: Probability space such that

(i)	$\mathcal{G} \subseteq \mathcal{F}$ is a D470: Subsigma-algebra of $\mathcal{F}$ on $\Omega$
(i)	$Z : \Omega \to \mathbb{C}$ be a D4877: Random complex number on $P$
(i)	\begin{equation} \mathbb{E} |Z| < \infty \end{equation}

Then \begin{equation} \mathbb{E}( \mathbb{E}(Z \mid \mathcal{G}) \mid \mathcal{G} ) \overset{a.s.}{=} \mathbb{E}(Z \mid \mathcal{G}) \end{equation}