diff --git a/README.md b/README.md
index 404fecb..e4e6a59 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,17 @@
 # VCF Compressor
 
-A simple bash script that compress images inside a vCard.
+A simple bash script that compress images inside a vCard 3.0.
+
+
+## Requirements
+
+* bash
+* imagemagick
+
+
+## Further reading
+
+* [vCard on Wikipedia](https://en.wikipedia.org/wiki/VCard)
+* vCard 3.0: [RFC 2425](https://tools.ietf.org/html/rfc2425) and [RFC 2426](https://tools.ietf.org/html/rfc2426)
+* vCard 4.0: [RFC 6350](https://tools.ietf.org/html/rfc6350)
+* CardDAV: [RFC 6352](https://tools.ietf.org/html/rfc6352)