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diff --git a/math/ieee/chap1/r4tx.f b/math/ieee/chap1/r4tx.f
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+c
+c-----------------------------------------------------------------------
+c subroutine:  r4tx
+c radix 4 iteration subroutine
+c-----------------------------------------------------------------------
+c
+      subroutine r4tx(nthpo, cr0, cr1, cr2, cr3, ci0, ci1, ci2, ci3)
+      dimension cr0(2), cr1(2), cr2(2), cr3(2), ci0(2), ci1(2), ci2(2),
+     *    ci3(2)
+      do 10 k=1,nthpo,4
+        r1 = cr0(k) + cr2(k)
+        r2 = cr0(k) - cr2(k)
+        r3 = cr1(k) + cr3(k)
+        r4 = cr1(k) - cr3(k)
+        fi1 = ci0(k) + ci2(k)
+        fi2 = ci0(k) - ci2(k)
+        fi3 = ci1(k) + ci3(k)
+        fi4 = ci1(k) - ci3(k)
+        cr0(k) = r1 + r3
+        ci0(k) = fi1 + fi3
+        cr1(k) = r1 - r3
+        ci1(k) = fi1 - fi3
+        cr2(k) = r2 - fi4
+        ci2(k) = fi2 + r4
+        cr3(k) = r2 + fi4
+        ci3(k) = fi2 - r4
+  10  continue
+      return
+      end