diff --git a/README.md b/README.md
index 1194fb3..13dad02 100644
--- a/README.md
+++ b/README.md
@@ -68,4 +68,3 @@ meson install -C build
 - [netlib/dfftpack1.0(fftpack4.0)](http://www.netlib.org/fftpack/)
 - [Documents of fft routines in GNU/gsl based on `netlib/fftpack`](https://www.gnu.org/software/gsl/doc/html/fft.html#)
 - [Documents of scipy.fftpack](https://docs.scipy.org/doc/scipy/reference/fftpack.html)
-- [NACR/FFTPACK 5.1](https://www2.cisl.ucar.edu/resources/legacy/fft5)