--- a/hws/Der.tex	Sun Sep 28 18:57:33 2025 +0100
+++ b/hws/Der.tex	Wed Oct 01 10:37:20 2025 +0100
@@ -38,7 +38,7 @@
 \noindent
 where $\Sigma^*$ is in our case the set of all strings (what follows in this section
 also holds for any kind of ``domain'', like the set of all integers or
-the set of all binary trees, etc). Let us assume $P(s)$ is a property that
+the set of all binary trees, etc).\footnote{NOTE: In the videos and slides I use \textit{UNIV} as notation for $\Sigma^*$. } Let us assume $P(s)$ is a property that
 is about strings, for example $P(s)$ could be ``the string $s$ has
 an even length'', or ``the string $s$ starts with the letter
 \texttt{a}''. Every such property carves out a subset of strings from