diff --git a/DESCRIPTION b/DESCRIPTION
index 67e77a3..2e6ca26 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -19,7 +19,7 @@ Imports:
     Ecume,
     mathjaxr,
     Rdpack,
-    readr,
+    readr (>= 2.0.0),
     rmarkdown,
     sf
 RdMacros: 
diff --git a/README.md b/README.md
index 65a4267..4756b9a 100644
--- a/README.md
+++ b/README.md
@@ -8,7 +8,16 @@
 [![licence](https://img.shields.io/badge/Licence-GPL--3-blue.svg)](https://www.r-project.org/Licenses/GPL-3) 
 <!-- badges: end -->
 
-## 1 Install
+## 1 Short description
+
+The main purpose of the `TDLM`'s package is to propose a rigorous framework to 
+fairly compare trip distribution laws and models as described in 
+[Lenormand et al. (2016)](doi:10.1016/j.jtrangeo.2015.12.008). This general
+framework is based on a two-step approach to generate mobility flows by 
+separating the trip distribution law, gravity or intervening opportunities, from 
+the modeling approach used to generate the flows from this law.
+
+## 2 Install
 
 The package `TDLM` can be installed with the following command line in R session:
 
@@ -25,15 +34,22 @@ or from GitHub
 devtools::install_github("EpiVec/TDLM", build_vignettes = TRUE)
 ```
 
-## 2 Tutorial
+## 3 Tutorial
 
 A tutorial vignette is available [here](https://epivec.github.io/TDLM/articles/TDLM.html).
 
-## 3 Dependencies
+## 4 Dependencies
 
 `TDLM` depends on `Ecume`, `mathjaxr`, `Rdpack`, `readr`, `rmarkdown` and `sf`.
 
-## 4  Citation
+## 5  Citation
 
 Lenormand M, Bassolas A & Ramasco JJ (2016) [Systematic comparison of trip distribution laws and models.](https://www.sciencedirect.com/science/article/abs/pii/S0966692315002422) *Journal of Transport Geography* 51, 158-169.
 
+## 6 Contribution instructions
+
+Please feel free to open an issue if you encounter a problem
+with the package.
+
+You can also reach me at maxime.lenormand[at]inrae.fr.
+
diff --git a/vignettes/TDLM.Rmd b/vignettes/TDLM.Rmd
index 1f81302..018c4d4 100644
--- a/vignettes/TDLM.Rmd
+++ b/vignettes/TDLM.Rmd
@@ -253,7 +253,7 @@ Finally, [county](https://epivec.github.io/TDLM/reference/county.html) is a
 spatial object containing the geometry of the 105 US Kansas counties in 2000. 
 
 ```{r}
-#library(sf)
+library(sf)
 
 data(county)