diff --git a/indexx.f b/indexx.f
new file mode 100644
index 000000000..464979742
--- /dev/null
+++ b/indexx.f
@@ -0,0 +1,19 @@
+      subroutine indexx(n,arr,indx)
+
+      parameter (NMAX=2000)
+      integer indx(n)
+      real arr(n)
+      real brr(NMAX)
+      if(n.gt.NMAX) then
+         print*,'n=',n,' too big in indexx.'
+         stop
+      endif
+      do i=1,n
+         brr(i)=arr(i)
+         indx(i)=i
+      enddo
+      call ssort(brr,indx,n,2)
+
+      return
+      end
+