v1.6.3.31 docs(links): add doi links in the references of the README file

Refs #66

DESCRIPTION

 Package: airGR
 Type: Package
 Title: Suite of GR Hydrological Models for Precipitation-Runoff Modelling
-Version: 1.6.3.30
+Version: 1.6.3.31
 Date: 2020-11-06
 Authors@R: c(
   person("Laurent", "Coron", role = c("aut", "trl"), comment = c(ORCID = "0000-0002-1503-6204")),

NEWS.md

@@ -4,7 +4,7 @@
 
 
 
-### 1.6.3.30 Release Notes (2020-11-06)
+### 1.6.3.31 Release Notes (2020-11-06)
 
 #### New features
 

README.md

@@ -61,15 +61,15 @@ For more information and to get started with the package, you can refer to the v
 
 ## References
 
-- Ficchi, A. (2017). An adaptive hydrological model for multiple time-steps: Diagnostics and improvements based on fluxes consistency. PhD thesis, Irstea (Antony), GRNE (Paris), France. 
-- Ficchi, A., C. Perrin and V. Andréassian (2019). Hydrological modelling at multiple sub-daily time steps: model improvement via flux-matching. Journal of Hydrology, 575, 1308-1327. doi: 10.1016/j.jhydrol.2019.05.084.
+- Ficchi, A. (2017). An adaptive hydrological model for multiple time-steps: Diagnostics and improvements based on fluxes consistency. PhD thesis, Irstea (Antony), GRNE (Paris), France.
+- Ficchi, A., C. Perrin and V. Andréassian (2019). Hydrological modelling at multiple sub-daily time steps: model improvement via flux-matching. Journal of Hydrology, 575, 1308-1327, doi: [10.1016/j.jhydrol.2019.05.084](https://www.doi.org/10.1016/j.jhydrol.2019.05.084).
 - Le Moine, N. (2008). Le bassin versant de surface vu par le souterrain : une voie d'amélioration des performances et du réalisme des modèles pluie-débit ?, PhD thesis (in French), UPMC - Cemagref Antony, Paris, France, 324 pp.
 - Mathevet, T. (2005). Quels modèles pluie-débit globaux pour le pas de temps horaire ? Développement empirique et comparaison de modèles sur un large échantillon de bassins versants, PhD thesis (in French), ENGREF - Cemagref Antony, Paris, France, 463 pp.
 - Mouelhi S. (2003). Vers une chaîne cohérente de modèles pluie-débit conceptuels globaux aux pas de temps pluriannuel, annuel, mensuel et journalier, PhD thesis (in French), ENGREF - Cemagref Antony, Paris, France, 323 pp.
-- Mouelhi, S., C. Michel, C. Perrin and V. Andréassian (2006a). Stepwise development of a two-parameter monthly water balance model, Journal of Hydrology, 318(1-4), 200-214, doi: 10.1016/j.jhydrol.2005.06.014.
-- Mouelhi, S., C. Michel, C. Perrin. & V. Andreassian (2006b). Linking stream flow to rainfall at the annual time step: the Manabe bucket model revisited, Journal of Hydrology, 328, 283-296, doi: 10.1016/j.jhydrol.2005.12.022.
-- Perrin, C., C. Michel and V. Andréassian (2003). Improvement of a parsimonious model for streamflow simulation, Journal of Hydrology, 279(1-4), 275-289, doi: 10.1016/S0022-1694(03)00225-7.
-- Pushpalatha, R., C. Perrin, N. Le Moine, T. Mathevet and V. Andréassian (2011). A downward structural sensitivity analysis of hydrological models to improve low-flow simulation, Journal of Hydrology, 411(1-2), 66-76, doi: 10.1016/j.jhydrol.2011.09.034.
-- Valéry, A., V. Andréassian and C. Perrin (2014). "As simple as possible but not simpler": What is useful in a temperature-based snow-accounting routine? Part 2 - Sensitivity analysis of the Cemaneige snow accounting routine on 380 catchments, Journal of Hydrology, 517(0): 1176-1187, doi: 1176-1187, doi: 10.1016/j.jhydrol.2014.04.058.
+- Mouelhi, S., C. Michel, C. Perrin and V. Andréassian (2006a). Stepwise development of a two-parameter monthly water balance model, Journal of Hydrology, 318(1-4), 200-214, doi: [10.1016/j.jhydrol.2005.06.014](https://www.doi.org/10.1016/j.jhydrol.2005.06.014).
+- Mouelhi, S., C. Michel, C. Perrin. and V. Andreassian (2006b). Linking stream flow to rainfall at the annual time step: the Manabe bucket model revisited, Journal of Hydrology, 328, 283-296, doi: [10.1016/j.jhydrol.2005.12.022](https://www.doi.org/10.1016/j.jhydrol.2005.12.022).
+- Perrin, C., C. Michel and V. Andréassian (2003). Improvement of a parsimonious model for streamflow simulation, Journal of Hydrology, 279(1-4), 275-289, doi: [10.1016/S0022-1694(03)00225-7](https://www.doi.org/10.1016/S0022-1694(03)00225-7).
+- Pushpalatha, R., C. Perrin, N. Le Moine, T. Mathevet and V. Andréassian (2011). A downward structural sensitivity analysis of hydrological models to improve low-flow simulation, Journal of Hydrology, 411(1-2), 66-76, doi: [10.1016/j.jhydrol.2011.09.034](https://www.doi.org/10.1016/j.jhydrol.2011.09.034).
+- Valéry, A., V. Andréassian and C. Perrin (2014). "As simple as possible but not simpler": What is useful in a temperature-based snow-accounting routine? Part 2 - Sensitivity analysis of the Cemaneige snow accounting routine on 380 catchments, Journal of Hydrology, 517(0): 1176-1187, doi: [10.1016/j.jhydrol.2014.04.058](https://www.doi.org/10.1016/j.jhydrol.2014.04.058).