--- /dev/null
+\documentclass{article}
+
+\usepackage{a4wide}
+\usepackage{amssymb}
+\usepackage{amsmath}
+\usepackage[all]{xypic}
+
+\newcommand{\ra}{\rightarrow}
+\newcommand{\un}{\text{ \textsf{U} }}
+\newcommand{\ev}{\lozenge}
+\newcommand{\al}{\square}
+\newcommand{\nx}{\bigcirc}
+
+\everymath{\displaystyle}
+
+\begin{document}
+\begin{enumerate}
+ \item
+ $\xymatrix{
+ & l_0 & l_1 & l_2 & l_3 & l_5 & l_6 & l_7\\
+ l_0\\
+ l_1\\
+ l_2\\
+ l_3\\
+ l_5\\
+ l_6\\
+ l_7
+ }$
+ \item
+ $\al(crit_0\veebar crit_1)$
+ \item
+ We define:\\
+ $ AP=\bigcup_{i\in N}\{lift_n, door_n,call_n\},
+ N=\{0, 1, 2, 3\}$
+ \begin{enumerate}
+ \item
+ $\bigwedge_{n\in N}\al(door_m\ra lift_n)$
+ \item
+ $\bigwedge_{n\in N}\al(call_n\ra\ev(lift_n\wedge door_n))$
+ \item
+ $\al\ev lift_0$
+ \item
+ $\al(call_3\rightarrow\bigcirc (lift_3\wedge door_3))$
+ \end{enumerate}
+ \item\strut\\
+ $\begin{array}{ll}
+ \varphi_1=\ev\al c &
+ s_2\ra s_4\overline{\ra s_5}\\
+ \varphi_2=\al\ev c &
+ s_2\ra s_4\overline{\ra s_5}\\
+ \varphi_3=\nx\neg c\rightarrow\nx\nx c &
+ s_2\ra s_4\overline{\ra s_5}\\
+ \varphi_4=\al a &
+ \text{Impossible. $a$ only holds in $s_1$ and in $s_5$.}\\
+ & \text{$s_1$ we can only leave through a state where $\neg a$}\\
+ & \text{$s_5$ we can not reach through $s_1$ without passing
+ through a $\neg a$ state}\\
+ \varphi_5=a\un\al(b\vee c) &
+ s_1\ra s_4\overline{\ra s_5}\\
+ \varphi_6=(\nx\nx b)\un(b\vee c) &
+ s_2\ra s_4\overline{\ra s_5}
+ \end{array}$
+\end{enumerate}
+\end{document}