update citations to include new JOSS paper (#570)

* update citations

* update whatsnew [skip ci]

Author: wholmgren

README.md

@@ -69,3 +69,18 @@ community. We also make new version announcements on the google group.
 If you suspect that you may have discovered a bug or if you'd like to
 change something about pvlib, then please make an issue on our
 [GitHub issues page](https://github.com/pvlib/pvlib-python/issues).
+
+
+Citing
+======
+
+If you use pvlib-python in a published work, please cite:
+
+  William F. Holmgren, Clifford W. Hansen, and Mark A. Mikofski.
+  "pvlib python: a python package for modeling solar energy systems."
+  Journal of Open Source Software, 3(29), 884, (2018).
+  https://doi.org/10.21105/joss.00884
+
+Please also cite the DOI corresponding to the specific version of
+pvlib-python that you used. pvlib-python DOIs are listed at
+[Zenodo.org](https://zenodo.org/search?page=1&size=20&q=conceptrecid:593284&all_versions&sort=-version)

docs/sphinx/source/index.rst

@@ -36,8 +36,18 @@ Citing pvlib-python
 
 Many of the contributors to pvlib-python work in institutions where
 citation metrics are used in performance or career evaluations. If you
-use pvlib-python in a published work, please cite the most appropriate
-of:
+use pvlib-python in a published work, please cite:
+
+  William F. Holmgren, Clifford W. Hansen, and Mark A. Mikofski.
+  "pvlib python: a python package for modeling solar energy systems."
+  Journal of Open Source Software, 3(29), 884, (2018).
+  https://doi.org/10.21105/joss.00884
+
+Please also cite the DOI corresponding to the specific version of
+pvlib-python that you used. pvlib-python DOIs are listed at
+`Zenodo.org <https://zenodo.org/search?page=1&size=20&q=conceptrecid:593284&all_versions&sort=-version>`_
+
+Additional pvlib-python publications include:
 
 * J. S. Stein, “The photovoltaic performance modeling
   collaborative (PVPMC),” in Photovoltaic Specialists Conference, 2012.
@@ -60,9 +70,6 @@ of:
   "An Open Source Solar Power Forecasting Tool Using PVLIB-Python,"
   in 43rd Photovoltaic Specialists Conference, 2016.
 
-Specific released versions of pvlib-python can be cited using their
-`Zenodo DOI <https://zenodo.org/search?ln=en&p=pvlib&action_search=>`_.
-
 
 Contents
 ========

docs/sphinx/source/whatsnew/v0.6.0.rst

@@ -172,6 +172,7 @@ Documentation
 * Add PVSystem documentation page. (:issue:`514`, :issue:`319`)
 * Add example of Kasten Linke Turbidity calculation, discuss broadband AOD and
   Angstrom Turbidity Model. (:issue:`302`)
+* Add JOSS paper to "Citing pvlib-python" section.
 
 
 Testing