Corrected dead link.

--- a/src/HOLCF/IOA/README.html	Mon Jul 13 16:43:57 1998 +0200
+++ b/src/HOLCF/IOA/README.html	Mon Jul 13 17:46:20 1998 +0200
@@ -22,7 +22,7 @@
    <li> A proof of a Network Transmission Protocol (NTP subdirectory) using the theory of IOA described above. For details see:<BR>
 
         Tobias Nipkow, Konrad Slind.
-<A HREF=http://www4.informatik.tu-muenchen.de/~nipkow/pubs/ioa.html>
+<A HREF=http://www4.informatik.tu-muenchen.de/~nipkow/pubs/types94.html>
 I/O Automata in Isabelle/HOL</A>. In <i>Types for Proofs and Programs</i>,
 LNCS 996, 1995, 101-119.