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diff --git a/math/ieee/chap1/r2tx.f b/math/ieee/chap1/r2tx.f
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+c
+c-----------------------------------------------------------------------
+c subroutine:  r2tx
+c radix 2 iteration subroutine
+c-----------------------------------------------------------------------
+c
+      subroutine r2tx(nthpo, cr0, cr1, ci0, ci1)
+      dimension cr0(2), cr1(2), ci0(2), ci1(2)
+      do 10 k=1,nthpo,2
+        r1 = cr0(k) + cr1(k)
+        cr1(k) = cr0(k) - cr1(k)
+        cr0(k) = r1
+        fi1 = ci0(k) + ci1(k)
+        ci1(k) = ci0(k) - ci1(k)
+        ci0(k) = fi1
+  10  continue
+      return
+      end