add longer description and citation

Author: cadenmyers13

README.rst

@@ -37,7 +37,13 @@
 
 Tool for visualizing 3D diffraction and PDF Images.
 
-* LONGER DESCRIPTION HERE
+* Diffpy.fourigui is a tool to visualize and process 3D data sets written with the Python programming language.
+Diffpy.fourigui always displays one slice perpendicular to one axis and allows scrolling through the 3D data set along
+the given axis with a slider. It shows feedback values such as global and local maxima, minima or NAN ratios.
+The matplotlib panel e.g. for zooming and saving figures is featured. Diffpy.fourigui is designed for the processing of 3D
+atomic pair distribution functions (PDFs). One can load a 3D reciprocal space scattering volume which can be Fourier
+transformed to the 3D PDF. Thereby, one can apply cut off frequencies beyond and below given Q values, compare the
+results and switch between the scattering volume in reciprocal space and 3D PDF in real space.
 
 For more information about the diffpy.fourigui library, please consult our `online documentation <https://diffpy.github.io/diffpy.fourigui>`_.
 
@@ -46,7 +52,10 @@ Citation
 
 If you use diffpy.fourigui in a scientific publication, we would like you to cite this package as
 
-        diffpy.fourigui Package, https://github.com/diffpy/diffpy.fourigui
+        S. Y. Harouna-Mayer, S. Tao, Z. Gong, M. v Zimmermann, D. Koziej, A.-C. Dippel, and S. J. L. Billinge
+        `Real-Space Texture and Pole-Figure Analysis Using the 3D Pair Distribution
+        Function on a Platinum Thin Film <https://doi.org/10.1107/S2052252522006674>`. IUCrJ 2022, 9 (5), 594–603.
+
 
 Installation
 ------------