diff --git a/docs/requirements.in b/docs/requirements.in
new file mode 100644
index 0000000..0d74803
--- /dev/null
+++ b/docs/requirements.in
@@ -0,0 +1,4 @@
+pip-tools==6.4.0
+sphinx==2.0.0
+sphinx-rtd-theme==0.4.3
+sphinxcontrib-plantuml==0.15