diff --git a/todo.md b/todo.md
index 259e7d6..0d28487 100644
--- a/todo.md
+++ b/todo.md
@@ -55,4 +55,10 @@
     * [ ] orbital state vectors
     * [ ] transfer orbits
         * [ ] hohmann
-        * [ ] brachistocrone
\ No newline at end of file
+        * [ ] brachistocrone
+
+* [ ] set up a git server w ssh
+    * [ ] https://www.inmotionhosting.com/support/website/git/git-server/
+    * [ ] https://www.inmotionhosting.com/support/product-guides/cloud-server/ssh-security-sftp-ubuntu-cloud-server/
+
+* [ ] real-time operating systems