diff --git a/20.08.json b/20.08.json
new file mode 100644
index 0000000..ef13bc2
--- /dev/null
+++ b/20.08.json
@@ -0,0 +1,38 @@
+{
+    "externals": [
+        {
+            "pushurl": "ssh://review.mlplatform.org:29418/ml/ethos-u/ethos-u-core-software",
+            "path": "core_software",
+            "fetchurl": "https://review.mlplatform.org/ml/ethos-u/ethos-u-core-software",
+            "revision": "20.08"
+        },
+        {
+            "pushurl": "ssh://review.mlplatform.org:29418/ml/ethos-u/ethos-u-core-driver",
+            "path": "core_software/core_driver",
+            "fetchurl": "https://review.mlplatform.org/ml/ethos-u/ethos-u-core-driver",
+            "revision": "20.08"
+        },
+        {
+            "path": "core_software/cmsis",
+            "fetchurl": "https://github.com/ARM-software/CMSIS_5.git",
+            "revision": "55a6a153cd8e208364db3502b6248392fdf59eaf"
+        },
+        {
+            "path": "core_software/tensorflow",
+            "fetchurl": "https://github.com/tensorflow/tensorflow",
+            "revision": "ff1ecf14de2b2728ca6d70ba7616700920b32c03"
+        },
+        {
+            "pushurl": "ssh://review.mlplatform.org:29418/ml/ethos-u/ethos-u-linux-driver-stack",
+            "path": "linux_driver_stack",
+            "fetchurl": "https://review.mlplatform.org/ml/ethos-u/ethos-u-linux-driver-stack",
+            "revision": "20.08"
+        },
+        {
+            "pushurl": "ssh://review.mlplatform.org:29418/ml/ethos-u/ethos-u-vela",
+            "path": "vela",
+            "fetchurl": "https://review.mlplatform.org/ml/ethos-u/ethos-u-vela",
+            "revision": "1.2.0"
+        }
+    ]
+}
diff --git a/README.md b/README.md
index 1a90c1e..cb26736 100644
--- a/README.md
+++ b/README.md
@@ -3,11 +3,25 @@
 This is the root repository for all Arm Ethos-U software. It is provided to help
 users download required repositories and place them in a tree structure.
 
+## Fetching externals
+
+The externals can be downloaded with a Python script. The default configuration
+is stored in `externals.json` which is a human readable JSON file.
+
 ```
 $ ./fetch_externals.py fetch
 ```
 
-The script will build following tree structure.
+The default configuration can be overriddend with the `-c` argument, for
+example.
+
+```
+$ ./fetch_externals.py -c 20.08.json fetch
+```
+
+## Directory structure
+
+The script will build following directory structure.
 
 ```
 Directory