diff --git a/src/spec.rs b/src/spec.rs
index e5846cc..80416c6 100644
--- a/src/spec.rs
+++ b/src/spec.rs
@@ -14,6 +14,7 @@ pub struct TinyEncryptConfig {
     pub pgp_encrypt_public_key_pem: Option<String>,
 }
 
+/// Specification: https://git.hatter.ink/hatter/tiny-encrypt-java/src/branch/master/TinyEncryptSpecV1.1.md
 #[derive(Clone, Debug, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct TinyEncryptMeta {