Merge pull request #45 from fortran-lang/edit-readme

Documentation updates

README.md

@@ -64,8 +64,19 @@ meson configure build --prefix=/path/to/install
 meson install -C build
 ```
 
-## Links
-- [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)
+## Documentation
+See the our [GitHub Pages site] for documentation generated by [FORD] from the fortran-lang/fftpack [project file].
+
+## References 
+Although fortran-lang is _not_ interface-compatible with any of the following libraries, each contains documentation that might be useful for different reasons:
+- **Recommended reference:** The [scipy.fftpack] documentation contains succinct description of the storage sequences for function results that match those in fortran-lang/fftpack, e.g., the location of the real and imaginary parts of the `rfft` function result.
+- **Theory reference:** The [documentation for the GNU/gsl FFT routines], which are also based on netlib/fftpack, provides some useful definitions of FFT terminology and represenations of the analytical forms of the Discrete Fourier Transform nicely formatted by [LaTeX].
+- **Historical reference:** The [netlib/fftpack] library on which fortran-lang/fftpack is useful for understanding several fortran-lang/fftpack design choices, e.g., the procedure dependencies.
+
+[FORD]: https://github.com/Fortran-FOSS-Programmers/ford
+[project file]: ./API-doc-FORD-file.md
+[scipy.fftpack]: https://docs.scipy.org/doc/scipy/reference/fftpack.html
+[documentation for the GNU/gsl FFT routines]: https://www.gnu.org/software/gsl/doc/html/fft.html#
+[netlib/fftpack]: http://www.netlib.org/fftpack/
+[LaTeX]: https://www.latex-project.org
+[GitHub Pages site]: https://fortran-lang.github.io/fftpack/