diff --git a/course_tools b/course_tools
new file mode 160000
index 0000000..ffef909
--- /dev/null
+++ b/course_tools
@@ -0,0 +1 @@
+Subproject commit ffef9096a4c74c0e85461b63cb946d607cf06c42
diff --git a/hw0-doc b/hw0-doc
new file mode 160000
index 0000000..b02aef3
--- /dev/null
+++ b/hw0-doc
@@ -0,0 +1 @@
+Subproject commit b02aef331c1911491064e0de64544c2ea43f7e4a
diff --git a/hw1-doc b/hw1-doc
new file mode 160000
index 0000000..7aef37f
--- /dev/null
+++ b/hw1-doc
@@ -0,0 +1 @@
+Subproject commit 7aef37f027ebb9f7cdf5712dc7ce6f8047470705
diff --git a/hw2-doc b/hw2-doc
new file mode 160000
index 0000000..4393462
--- /dev/null
+++ b/hw2-doc
@@ -0,0 +1 @@
+Subproject commit 4393462db150e94227ce4f1ef6398e5cc1884cf1
diff --git a/hw3-doc b/hw3-doc
new file mode 160000
index 0000000..5fa872a
--- /dev/null
+++ b/hw3-doc
@@ -0,0 +1 @@
+Subproject commit 5fa872a5b6b9bcc38a721bb3696f53ead2c09cdc
diff --git a/hw4-doc b/hw4-doc
new file mode 160000
index 0000000..744ad02
--- /dev/null
+++ b/hw4-doc
@@ -0,0 +1 @@
+Subproject commit 744ad02c6af07a8e2b76fc43280b9de35277b25c
diff --git a/reference_doc b/reference_doc
new file mode 160000
index 0000000..2ff0124
--- /dev/null
+++ b/reference_doc
@@ -0,0 +1 @@
+Subproject commit 2ff01245818dc7bf48a43256df4096c40e55e279