diff --git a/CustomMath_lib/Matrix/Matrix.h b/CustomMath_lib/Matrix/Matrix.h
index a302015..3f5ff0c 100644
--- a/CustomMath_lib/Matrix/Matrix.h
+++ b/CustomMath_lib/Matrix/Matrix.h
@@ -87,7 +87,7 @@ class Matrix {
     [[nodiscard]] Matrix sub_lowerTriangle() const;
 
     /// Set the sub-matrix of the matrix [start, end) x [start, end), both use index that start from 0
-    /// \warning this is often used in conjunction with sub_matrix() to set a sub-matrix to another matrix
+    /// \warning this is often used in conjunction with sub_matrix()
     void set(ull start_row, ull end_row, ull start_col, ull end_col, const Matrix &other);
 
     /*
@@ -112,7 +112,7 @@ class Matrix {
     /// A.rows == A.cols
     [[nodiscard]] bool isSquare() const;
 
-    /// (a_{ij}^2)^(1/2)
+    /// 2-norm
     [[nodiscard]] lld norm() const;
 
     /// min{a_{ij}}
diff --git a/CustomMath_lib/Vector/Vector.cpp b/CustomMath_lib/Vector/Vector.cpp
index 50cafe8..d1382bd 100644
--- a/CustomMath_lib/Vector/Vector.cpp
+++ b/CustomMath_lib/Vector/Vector.cpp
@@ -157,6 +157,10 @@ lld Vector::operator*(const Vector &other) const {
     return result;
 }
 
+Vector operator*(lld scalar, const Vector &vector) {
+    return vector * scalar;
+}
+
 bool Vector::operator==(const Vector &other) const {
     if (this->size != other.size) {
         return false;
diff --git a/CustomMath_lib/Vector/Vector.h b/CustomMath_lib/Vector/Vector.h
index beab20d..dae5b5e 100644
--- a/CustomMath_lib/Vector/Vector.h
+++ b/CustomMath_lib/Vector/Vector.h
@@ -18,39 +18,57 @@ class Vector {
     /// Copy constructor
     Vector(const Vector &other);
 
+    /// size, 0
     explicit Vector(ull size);
 
+    /// size, default_value
     explicit Vector(ull size, lld default_value);
 
+    /// size, [lower_bound, upper_bound]
     explicit Vector(ull size, double lower_bound, double upper_bound);
 
+    /// 1d vector
     explicit Vector(const std::vector<lld> &array);
 
+    /// \warning this constructor is not robust / time-efficient
     explicit Vector(std::string matlab_array);
 
+    /// Return a sub-vector of this vector [start, end)
     [[nodiscard]] Vector sub_vector(ull start, ull end) const;
 
+    /// Set a sub-vector of this vector [start, end)
+    /// \warning this is often used in conjunction with sub_vector()
     void set(ull start, ull end, const Vector &other);
 
+    /// Print the vector
     void print();
 
+    /// u == v
+    [[nodiscard]] bool operator==(const Vector &other) const;
+
+    /// 2-norm
+    [[nodiscard]] lld norm() const;
+
+    /// u + v
     [[nodiscard]] Vector operator+(const Vector &other) const;
 
+    /// u - v
     [[nodiscard]] Vector operator-(const Vector &other) const;
 
+    /// u * v -> Real
     [[nodiscard]] lld operator*(const Vector &other) const;
 
+    /// u * scalar
     [[nodiscard]] Vector operator*(lld scalar) const;
 
+    /// u / scalar
     [[nodiscard]] Vector operator/(lld scalar) const;
-
-    [[nodiscard]] bool operator==(const Vector &other) const;
-
-    [[nodiscard]] lld norm() const;
 };
 
+/// [1,2,3,0,2] -> [1,1,1,0,1]
 Vector sign(const Vector &vector);
 
+/// scalar * u
 Vector operator*(lld scalar, const Vector &vector);
 
 #endif //NUMERICAL_ALGEBRA_VECTOR_H