diff --git a/academic_codes/2021.07.19_calculate_reciprocal_lattice_vectors/calculate_reciprocal_lattice_vectors.py b/academic_codes/2021.07.19_calculate_reciprocal_lattice_vectors/calculate_reciprocal_lattice_vectors.py
index 14099a4..6107c8f 100644
--- a/academic_codes/2021.07.19_calculate_reciprocal_lattice_vectors/calculate_reciprocal_lattice_vectors.py
+++ b/academic_codes/2021.07.19_calculate_reciprocal_lattice_vectors/calculate_reciprocal_lattice_vectors.py
@@ -1,3 +1,8 @@
+"""
+This code is supported by the website: https://www.guanjihuan.com
+The newest version of this code is on the web page: https://www.guanjihuan.com/archives/15978
+"""
+
 import numpy as np
 from math import *
 
diff --git a/academic_codes/2021.07.19_calculate_reciprocal_lattice_vectors/calculate_reciprocal_lattice_vectors_with_sympy.py b/academic_codes/2021.07.19_calculate_reciprocal_lattice_vectors/calculate_reciprocal_lattice_vectors_with_sympy.py
index dbf0123..40bf976 100644
--- a/academic_codes/2021.07.19_calculate_reciprocal_lattice_vectors/calculate_reciprocal_lattice_vectors_with_sympy.py
+++ b/academic_codes/2021.07.19_calculate_reciprocal_lattice_vectors/calculate_reciprocal_lattice_vectors_with_sympy.py
@@ -1,3 +1,8 @@
+"""
+This code is supported by the website: https://www.guanjihuan.com
+The newest version of this code is on the web page: https://www.guanjihuan.com/archives/15978
+"""
+
 import sympy