diff --git a/graphics/data-flow.pdf b/graphics/data-flow.pdf
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index 92662c1..0000000
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diff --git a/graphics/lmdk-scenario.pdf b/graphics/problem/lmdk-scenario.pdf
similarity index 100%
rename from graphics/lmdk-scenario.pdf
rename to graphics/problem/lmdk-scenario.pdf
diff --git a/graphics/lmdk-skip.pdf b/graphics/problem/lmdk-skip.pdf
similarity index 100%
rename from graphics/lmdk-skip.pdf
rename to graphics/problem/lmdk-skip.pdf
diff --git a/graphics/lmdk-uniform.pdf b/graphics/problem/lmdk-uniform.pdf
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rename from graphics/lmdk-uniform.pdf
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diff --git a/graphics/st-cont.pdf b/graphics/problem/st-cont.pdf
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diff --git a/text/problem/thething/main.tex b/text/problem/thething/main.tex
index 90f9788..190cf3b 100644
--- a/text/problem/thething/main.tex
+++ b/text/problem/thething/main.tex
@@ -18,7 +18,7 @@ Example~\ref{ex:scenario} shows the result of user--LBS interaction while retrie
 
   \begin{figure}[htp]
     \centering
-    \includegraphics[width=\linewidth]{lmdk-scenario}
+    \includegraphics[width=\linewidth]{problem/lmdk-scenario}
     \caption{A time series with {\thethings} (highlighted in gray).
     }
     \label{fig:scenario}
@@ -59,7 +59,7 @@ Last but not least, {\thethings} in \emph{smart grid} electricity usage patterns
 
   \begin{figure}[htp]
     \centering
-    \includegraphics[width=\linewidth]{st-cont}
+    \includegraphics[width=\linewidth]{problem/st-cont}
     \caption{User-level and {\thething} $\varepsilon$-differential privacy protection for the time series of Figure~\ref{fig:scenario}.}
     \label{fig:st-cont}
   \end{figure}
diff --git a/text/problem/thething/solution.tex b/text/problem/thething/solution.tex
index 586b5d3..fe6b130 100644
--- a/text/problem/thething/solution.tex
+++ b/text/problem/thething/solution.tex
@@ -16,7 +16,7 @@ Consequently, at each timestamp we protect every {\thething}, while reserving a
 
 \begin{figure}[htp]
   \centering
-  \includegraphics[width=0.9\linewidth]{lmdk-uniform}
+  \includegraphics[width=0.9\linewidth]{problem/lmdk-uniform}
   \caption{Uniform application scenario of {\thething} privacy.}
   \label{fig:lmdk-uniform}
 \end{figure}
@@ -32,7 +32,7 @@ Particularly, sporadic location data publishing~\cite{gambs2010show, russell2018
 
 \begin{figure}[htp]
   \centering
-  \includegraphics[width=0.9\linewidth]{lmdk-skip}
+  \includegraphics[width=0.9\linewidth]{problem/lmdk-skip}
   \caption{Application scenario of the Skip model in {\thething} privacy.}
   \label{fig:lmdk-skip}
 \end{figure}