diff --git a/DIRECTORY.md b/DIRECTORY.md
index 4e67ad515..72133a60b 100644
--- a/DIRECTORY.md
+++ b/DIRECTORY.md
@@ -86,6 +86,7 @@
 
 ## Computer Vision
   * [Harriscorner](https://github.com/TheAlgorithms/Python/blob/master/computer_vision/harriscorner.py)
+  * [Meanthreshold](https://github.com/TheAlgorithms/Python/blob/master/computer_vision/meanthreshold.py)
 
 ## Conversions
   * [Binary To Decimal](https://github.com/TheAlgorithms/Python/blob/master/conversions/binary_to_decimal.py)
@@ -139,6 +140,7 @@
     * [Circular Linked List](https://github.com/TheAlgorithms/Python/blob/master/data_structures/linked_list/circular_linked_list.py)
     * [Deque Doubly](https://github.com/TheAlgorithms/Python/blob/master/data_structures/linked_list/deque_doubly.py)
     * [Doubly Linked List](https://github.com/TheAlgorithms/Python/blob/master/data_structures/linked_list/doubly_linked_list.py)
+    * [Doubly Linked List Two](https://github.com/TheAlgorithms/Python/blob/master/data_structures/linked_list/doubly_linked_list_two.py)
     * [From Sequence](https://github.com/TheAlgorithms/Python/blob/master/data_structures/linked_list/from_sequence.py)
     * [Has Loop](https://github.com/TheAlgorithms/Python/blob/master/data_structures/linked_list/has_loop.py)
     * [Is Palindrome](https://github.com/TheAlgorithms/Python/blob/master/data_structures/linked_list/is_palindrome.py)
@@ -157,6 +159,7 @@
   * Stacks
     * [Balanced Parentheses](https://github.com/TheAlgorithms/Python/blob/master/data_structures/stacks/balanced_parentheses.py)
     * [Dijkstras Two Stack Algorithm](https://github.com/TheAlgorithms/Python/blob/master/data_structures/stacks/dijkstras_two_stack_algorithm.py)
+    * [Evaluate Postfix Notations](https://github.com/TheAlgorithms/Python/blob/master/data_structures/stacks/evaluate_postfix_notations.py)
     * [Infix To Postfix Conversion](https://github.com/TheAlgorithms/Python/blob/master/data_structures/stacks/infix_to_postfix_conversion.py)
     * [Infix To Prefix Conversion](https://github.com/TheAlgorithms/Python/blob/master/data_structures/stacks/infix_to_prefix_conversion.py)
     * [Linked Stack](https://github.com/TheAlgorithms/Python/blob/master/data_structures/stacks/linked_stack.py)
@@ -655,6 +658,8 @@
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_055/sol1.py)
   * Problem 056
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_056/sol1.py)
+  * Problem 057
+    * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_057/sol1.py)
   * Problem 062
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_062/sol1.py)
   * Problem 063
@@ -667,12 +672,17 @@
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_071/sol1.py)
   * Problem 072
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_072/sol1.py)
+    * [Sol2](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_072/sol2.py)
   * Problem 074
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_074/sol1.py)
+  * Problem 075
+    * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_075/sol1.py)
   * Problem 076
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_076/sol1.py)
   * Problem 080
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_080/sol1.py)
+  * Problem 091
+    * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_091/sol1.py)
   * Problem 097
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_097/sol1.py)
   * Problem 099
@@ -689,6 +699,8 @@
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_125/sol1.py)
   * Problem 173
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_173/sol1.py)
+  * Problem 174
+    * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_174/sol1.py)
   * Problem 191
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_191/sol1.py)
   * Problem 234
@@ -698,6 +710,7 @@
   * [Validate Solutions](https://github.com/TheAlgorithms/Python/blob/master/project_euler/validate_solutions.py)
 
 ## Quantum
+  * [Half Adder](https://github.com/TheAlgorithms/Python/blob/master/quantum/half_adder.py)
   * [Not Gate](https://github.com/TheAlgorithms/Python/blob/master/quantum/not_gate.py)
   * [Quantum Entanglement](https://github.com/TheAlgorithms/Python/blob/master/quantum/quantum_entanglement.py)
   * [Single Qubit Measure](https://github.com/TheAlgorithms/Python/blob/master/quantum/single_qubit_measure.py)
diff --git a/quantum/half_adder.py b/quantum/half_adder.py
index 1310edbbf..4af704e64 100755
--- a/quantum/half_adder.py
+++ b/quantum/half_adder.py
@@ -6,8 +6,8 @@ the sum and carry qubits, observed over 1000 runs of the experiment
 .
 
 References:
-- https://en.wikipedia.org/wiki/Adder_(electronics)
-- https://qiskit.org/textbook/ch-states/atoms-computation.html#4.2-Remembering-how-to-add-
+https://en.wikipedia.org/wiki/Adder_(electronics)
+https://qiskit.org/textbook/ch-states/atoms-computation.html#4.2-Remembering-how-to-add-
 """
 
 import qiskit as q