diff --git a/src/wurstsalat_generator_pro/substrings.rs b/src/wurstsalat_generator_pro/substrings.rs
index 58eb1f7..283883a 100644
--- a/src/wurstsalat_generator_pro/substrings.rs
+++ b/src/wurstsalat_generator_pro/substrings.rs
@@ -1,3 +1,7 @@
+// SPDX-FileCopyrightText: 2025 @iadd
+// SPDX-FileContributor: @iadd
+//
+// SPDX-License-Identifier: MIT
 use std::{collections::HashMap, str::CharIndices};
 
 #[derive(Copy, Clone, Debug, Default, PartialEq, Eq, Hash)]