diff --git a/arch/ia64/lib/idiv32.S b/arch/ia64/lib/idiv32.S
index 2ac28bf..c91b5b0 100644
--- a/arch/ia64/lib/idiv32.S
+++ b/arch/ia64/lib/idiv32.S
@@ -11,7 +11,7 @@
  *
  * For more details on the theory behind these algorithms, see "IA-64
  * and Elementary Functions" by Peter Markstein; HP Professional Books
- * (http://www.hp.com/go/retailbooks/)
+ * (http://www.goodreads.com/book/show/2019887.Ia_64_and_Elementary_Functions)
  */
 
 #include <asm/asmmacro.h>
diff --git a/arch/ia64/lib/idiv64.S b/arch/ia64/lib/idiv64.S
index f69bd2b..627573c 100644
--- a/arch/ia64/lib/idiv64.S
+++ b/arch/ia64/lib/idiv64.S
@@ -11,7 +11,7 @@
  *
  * For more details on the theory behind these algorithms, see "IA-64
  * and Elementary Functions" by Peter Markstein; HP Professional Books
- * (http://www.hp.com/go/retailbooks/)
+ * (http://www.goodreads.com/book/show/2019887.Ia_64_and_Elementary_Functions)
  */
 
 #include <asm/asmmacro.h>