diff --git a/registry.go b/registry.go
index 392dcfc..2ba405a 100644
--- a/registry.go
+++ b/registry.go
@@ -78,6 +78,7 @@ func Credential(store Store) func(context.Context, string) (auth.Credential, err
 func mapStoreRegistryName(registry string) string {
 	// The Docker CLI expects that the 'docker.io' credential
 	// will be added under the key "https://index.docker.io/v1/"
+	// See: https://github.com/moby/moby/blob/master/registry/config.go#L25-L48
 	if registry == "docker.io" {
 		return "https://index.docker.io/v1/"
 	}
@@ -87,6 +88,7 @@ func mapStoreRegistryName(registry string) string {
 func mapAuthenticationRegistryName(hostname string) string {
 	// It is expected that the traffic targetting "registry-1.docker.io"
 	// will be redirected to "https://index.docker.io/v1/"
+	// See: https://github.com/moby/moby/blob/master/registry/config.go#L25-L48
 	if hostname == "registry-1.docker.io" {
 		return "https://index.docker.io/v1/"
 	}