privacy: Reference to the local variant of dp

text/preliminaries/privacy.tex

@@ -177,6 +177,9 @@ The privacy budget $\varepsilon$ is a positive real number that represents the u
 As the definition implies, $\mathcal{M}$ achieves stronger privacy protection for lower values of $\varepsilon$ since the probabilities of $D$ and $D'$ being true worlds are similar, but the utility of $\pmb{o}$ is reduced since more randomness is introduced by $\mathcal{M}$.
 The privacy budget $\varepsilon$ is usually set to $0.01$, $0.1$, or, in some cases, $\ln2$ or $\ln3$~\cite{lee2011much}.
 
+Its local variant~\cite{duchi2013local} is compatible with microdata, where $D$ is composed of a single data item $x$.
+We refer the interested reader to~\cite{desfontaines2020sok} for a systematic taxonomy of the different variants and extensions of differential privacy.
+
 \begin{definition}
   [Query function sensitivity]
   \label{def:qry-sens}