diff --git a/README.md b/README.md
index 6aa2dd9..5884473 100644
--- a/README.md
+++ b/README.md
@@ -5,11 +5,11 @@ This site contains some of the material of the course CB2030, including:
 
 * the [schedule](https://statisticalbiotechnology.github.io/cb2030/general/schedule) of the course  
 * the [prerequisites](https://statisticalbiotechnology.github.io/cb2030/general/prerequisites) in terms of knowledge for the course  
-* instruction for the [preparations](prep/readme) needed before each questions and answer session  
-* previous years [questions and answers](qa/readme)
+* instruction for the [preparations](prep/readme.md) needed before each questions and answer session  
+* previous years [questions and answers](qa/readme.md)
 * this years [questions](questions/)
-* the jupyter [notebooks](nb/readme)  
-* the [lab instructions](lab/readme)
+* the jupyter [notebooks](nb/readme.md)  
+* the [lab instructions](lab/readme.md)
 
 If you are inside the github repository you can reach the html version of the text [here](https://statisticalbiotechnology.github.io/cb2030/)