correction on which proof line used

Author: yiannis-had

content/normal-modal-logic/axioms-systems/proofs-modal-systems.tex

@@ -51,7 +51,7 @@
         with $\Box!A$ for $p$\\
         3. & $\Log{KDB4} \Proves \Box\Box!A \lif !A$ & \PL 1, 2\\
         4. &  $\Log{KDB4} \Proves \Box!A \lif \Box\Box!A$ & \Ax{4} \\
-        5. & $\Log{KDB4} \Proves \Box!A \lif !A$ & \PL, 1, 4. \\
+        5. & $\Log{KDB4} \Proves \Box!A \lif !A$ & \PL, 4, 3. \\
       \end{derivation}
     \item $\Log{KB4} \Proves \Ax{5}$:
       \begin{derivation}