diff --git a/ChangeLog b/ChangeLog
index 0a0f4ecde..6b9601724 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2010-05-11  Werner Lemberg  <wl@gnu.org>
+
+	* docs/formats.txt: Give pointer to PCF documentation.
+	Information provided by Alan Coopersmith
+	<alan.coopersmith@oracle.com>.
+
 2010-05-10  Ken Sharp  <ken.sharp@artifex.com>
 
 	Fix Savannah bug #29846.
diff --git a/docs/formats.txt b/docs/formats.txt
index c64d6d04f..efec66060 100644
--- a/docs/formats.txt
+++ b/docs/formats.txt
@@ -143,9 +143,17 @@ MAC  ---     PS     TYPE_1  ---        type1    T1_SPEC.pdf
 
 [3] Support is rudimentary currently; some tables are not loaded yet.
 
-[4] There is no formal PCF specification; you have to deduce the exact
-    format from the source code within X11.  George Williams did this for
-    his FontForge editor:
+[4] See
+
+      THE X WINDOW SYSTEM SERVER: X VERSION 11, RELEASE 5
+      Elias Israel, Erik Fortune, Digital Press, 1992
+      ISBN 1-55558-096-3
+
+    for a specification  given in Appendix D on pgs. 436-450.   However,
+    this information  might be out of  date; unfortunately,  there is no
+    PCF  specification available  online, and this book is out of print. 
+    George  Williams deduced  the font  format from the X11  sources and
+    documented it for his FontForge font editor:
 
       http://fontforge.sourceforge.net/pcf-format.html