diff --git a/mop_dna/PoN/README.md b/mop_dna/PoN/README.md
new file mode 100644
index 0000000..8a86c90
--- /dev/null
+++ b/mop_dna/PoN/README.md
@@ -0,0 +1,2 @@
+#please download and unzip the following repo:
+wget -b http://www.bio8.cs.hku.hk/clairs-to/databases/clairs-to_databases.tar.gz