diff --git a/index.markdown b/index.markdown
index 4bae8ba..aa38f64 100644
--- a/index.markdown
+++ b/index.markdown
@@ -52,10 +52,10 @@ Students should be able to understand the relationship between algorithm design,
 - __27 Oct 23__: Average time complexity and analysis of the quicksort algorithm ([4-average-time.pdf - pages 20-32](slides/4-average-time.pdf)); Randomised algorithms ([4-average-time.pdf - pages 33-40](slides/4-average-time.pdf)); Amortised analysis and the aggregate method ([5-amortised.pdf - pages 1-11](slides/5-amortised.pdf))
 - __10 Nov 23__: Test (30%): 9h30-10h30 (Specification, Correction, Worst/Best time analysis, Asymptotic analysis); Rest of the lesson starts at 11h15 - Amortised analysis ([5-amortised.pdf - pages 11-26](slides/5-amortised.pdf))
 - __17 Nov 23__: Amortised analysis ([5-amortised.pdf - pages 27-44](slides/5-amortised.pdf)); Data structures: sequences ([6-data-structures.pdf - pages 1-8](slides/6-data-structures.pdf))
-- __24 Nov 23__: Data structures: buffers and dictionaries
+- __24 Nov 23__: Data structures: buffers and dictionaries ([6-data-structures.pdf - pages 9-28](slides/6-data-structures.pdf))
 - __1 Dec 23__: _Holiday_
 - __8 Dec 23__: _Holiday_
-- __15 Dec 23__: Test (70%): 9h30-11h30 (all topics); no lesson after the test
+- __15 Dec 23__: Improvement test (70%): 9h30-11h30 (focused on average-time, amortised time, and data structures, but all topics can be asked); no lesson after the test
 
 
 
diff --git a/slides/6-data-structures.pdf b/slides/6-data-structures.pdf
index a88c086..e7341e3 100644
Binary files a/slides/6-data-structures.pdf and b/slides/6-data-structures.pdf differ
diff --git a/slides/6-data-structures.tex b/slides/6-data-structures.tex
index c033979..902a8e5 100755
--- a/slides/6-data-structures.tex
+++ b/slides/6-data-structures.tex
@@ -205,7 +205,7 @@ \section{Sets and Sequences}
   LInt pt = l;
   while (pt != NULL) pt = pt->next;
   pt = malloc(sizeof(struct list));
-  pt -> next = x;
+  pt -> value = x;
   pt -> next = NULL ;
   return l ;
 }
@@ -249,10 +249,10 @@ \section{Sets and Sequences}
   while (pt != NULL) {
     prev = pt; pt = pt->next; }
   pt = malloc(sizeof(struct list));
-  pt->next = x;
+  pt->value = x;
   pt->next = NULL ;
   if (l==NULL)  l = pt;
-  else prev->prox = pt;
+  else prev->next = pt;
   return l;
 }
 \end{lstlisting}
@@ -492,7 +492,7 @@ \section{Buffers (stacks and queueus)}
 %
 \begin{itemize}
   \item Binary tree
-  \item Each node is larger than any of its children
+  \item Each node is smaller than any of its children
   \item Implemented as an array
 \end{itemize}
 %
@@ -771,6 +771,8 @@ \section{Dictionaries}
 \\What is their complexity?}
 \end{frame}
 
+\section{Dictionaries with trees -- not for evaluation}
+
 % \section{Balanced trees}
 
 \begin{frame}\frametitle{More dictionaries: balanced trees}
@@ -807,7 +809,6 @@ \section{Dictionaries}
 
 \end{frame}
 
-
 \begin{frame}\frametitle{Binary Balanced Search Trees}
 
   \begin{columns}[t]