\begin{figure}[h!]
\centering
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    \rput{90}(0.8,2.4){$\hat{p}_1(u_i|t)$}
    \rput{90}(1.2,2.4){(Algorithm 1)}
    \rput[c](4.2,-0.2){$\hat{p}_2(u_i|t)$}
    \rput[c](4.2,-0.6){(Algorithm 2)}

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    \rput{-60}(6.1,1.4){$1^{st}$ Pareto frontier}

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    \rput{-60}(4.85,1.4){$2^{nd}$ Pareto frontier}

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    \rput[c](4.1,0.7){$*$}
    \rput{-60}(4.1,1.4){$3^{rd}$ Pareto frontier}

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\caption{User-Interest space given two different recommendation algorithms. Points are possible items and are represented by the relevance level estimated by different algorithms. Non-dominated items form successive Pareto frontiers.}
\label{fig:ex2}
\end{figure}
