fix links

external/contribute/vscode/vscode.md

@@ -59,7 +59,7 @@ For each how-to card, it is strongly recommended to create a new branch.
 
 ## Step 4: Write the procedure in Markdown
 
-If you need more details on how to do this, refer to the [corresponding howto-card](.../write-markdown).
+If you need more details on how to do this, refer to the [corresponding howto-card](/?contribute:markdown).
 
 ## Step 5: Commit your changes
 

external/general/remote-working/remote-working.md

@@ -25,7 +25,7 @@ via [Virtual Private Network (VPN)](http://vpn.uni.lu). All details are given [h
 ## Instant messaging
 
 One of the recommended tools to communicate is Slack. Each research group can sign up for free and
-create their own Slack instance on [slack.com](www.slack.com).
+create their own Slack instance on [slack.com](https://www.slack.com).
 
 ## Video conferencing and virtual meetings