diff --git a/Readme.md b/Readme.md
index 174e30a..e2dcae1 100644
--- a/Readme.md
+++ b/Readme.md
@@ -157,7 +157,7 @@ We chose to not use this design anymore as such a soft but small valve, while pr
 
 ### 4.d - _Older version :_ Short explanation of parameters
 
-As with the latest version, parameters are color coded, as is explained in the begining of the **Spreadsheet**.
+As with the latest version, parameters are color coded, as is explained in the begining of the **Spreadsheet** within the _Freecad_ file [3Dfiles/older_version/gas_mask_v6.FCStd](./3Dfiles/older_version/).
 
 Structural parameters are largely the same between this version and the newest version.