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diff --git a/math/ieee/chap1/r4syn.f b/math/ieee/chap1/r4syn.f
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+c
+c-----------------------------------------------------------------------
+c subroutine:  r4syn
+c radix 4 synthesis
+c-----------------------------------------------------------------------
+c
+      subroutine r4syn(int, b0, b1, b2, b3)
+      dimension b0(2), b1(2), b2(2), b3(2)
+      do 10 k=1,int
+        t0 = b0(k) + b1(k)
+        t1 = b0(k) - b1(k)
+        t2 = b2(k) + b2(k)
+        t3 = b3(k) + b3(k)
+        b0(k) = t0 + t2
+        b2(k) = t0 - t2
+        b1(k) = t1 + t3
+        b3(k) = t1 - t3
+  10  continue
+      return
+      end