--- users_guide.in.orig	2011-05-28 02:11:57.000000000 +0400
+++ users_guide.in	2013-04-13 14:16:37.000000000 +0400
@@ -164,7 +164,10 @@
 crimelab.com but now it appears the only source is ftp.bellcore.com. I
 suggest you try a web search for s/key source code.
 
-Note: S/KEY is a trademark of Bell Communications Research (Bellcore).
+To use OPIE, you must have built tac_plus with the -DWITH_OPIE flag.
+
+Note: S/KEY and OPIE are a trademark of Bell Communications Research 
+(Bellcore).
 
 Should you need them, there are routines for accessing password files
 (getpwnam,setpwent,endpwent,setpwfile) in pw.c.
@@ -414,7 +417,16 @@
       login = skey
     }
 
-4). Authentication using PAM (Pluggable Authentication Modules)
+4). Authentication using opie.
+
+If you have successfully built tac_plus with opie support, you can specify
+a user be authenticated via opie, as follows:
+
+    user = marcus {
+      login = opie
+    }
+
+5). Authentication using PAM (Pluggable Authentication Modules)
 
 Assuming that your OS supports it, tac_plus can be configured to use PAM
 for authentication, which may make it possible to use LDAP, SecureID, etc