diff --git a/examples/inner_test.py b/examples/inner_test.py
index d5e0f6b..d0de7e3 100644
--- a/examples/inner_test.py
+++ b/examples/inner_test.py
@@ -1,3 +1,19 @@
+#
+# Copyright (c) 2025 Fedir Kovalov.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, version 3.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+
 import shadowtube.preprocess as prep
 import shadowtube.recommend as rec
 
diff --git a/examples/tkinter_preview.py b/examples/tkinter_preview.py
index cda311d..0147246 100644
--- a/examples/tkinter_preview.py
+++ b/examples/tkinter_preview.py
@@ -1,3 +1,19 @@
+#
+# Copyright (c) 2025 Fedir Kovalov.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, version 3.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+
 import requests
 from io import BytesIO
 from PIL import Image, ImageTk
diff --git a/shadowtube/__init__.py b/shadowtube/__init__.py
index 4607170..51027ac 100644
--- a/shadowtube/__init__.py
+++ b/shadowtube/__init__.py
@@ -1,2 +1,18 @@
+#
+# Copyright (c) 2025 Fedir Kovalov.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, version 3.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+
 from .preprocess import *
 from .recommend import *
diff --git a/shadowtube/history.py b/shadowtube/history.py
new file mode 100644
index 0000000..fbc2766
--- /dev/null
+++ b/shadowtube/history.py
@@ -0,0 +1,18 @@
+class History: #Abstract class
+    def __init__(self, filename):
+        self.history = list() 
+        
+    def __size__(self):
+        return len(history)
+        
+    def parse_history(self, filename):
+        return history
+
+    def is_this_type(self, filename): # bool function, 
+        return false                  # returns false if Youtube history
+
+    def get_video(self, index):
+        return history[index]
+
+    def __iter__(self):
+        return iter(history)
diff --git a/shadowtube/preprocess.py b/shadowtube/preprocess.py
index 5f2cd88..59a132e 100644
--- a/shadowtube/preprocess.py
+++ b/shadowtube/preprocess.py
@@ -1,3 +1,19 @@
+#
+# Copyright (c) 2025 Fedir Kovalov.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, version 3.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+
 import json
 import math
 from typing import List
diff --git a/shadowtube/recommend.py b/shadowtube/recommend.py
index 7fcdbed..543bd67 100644
--- a/shadowtube/recommend.py
+++ b/shadowtube/recommend.py
@@ -1,3 +1,19 @@
+#
+# Copyright (c) 2025 Fedir Kovalov.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, version 3.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+
 import sqlite3
 from random import sample