diff --git a/fr/alnotz/Application.java b/fr/alnotz/Application.java
index e526f0a..3a2ff18 100644
--- a/fr/alnotz/Application.java
+++ b/fr/alnotz/Application.java
@@ -3,5 +3,6 @@ package fr.alnotz;
 public class Application {
     public static void main(String[] args){
         System.out.println("Hi.");
+
     }
 }
diff --git a/fr/alnotz/Dual.java b/fr/alnotz/Dual.java
index 40c4aa1..defb25c 100644
--- a/fr/alnotz/Dual.java
+++ b/fr/alnotz/Dual.java
@@ -3,6 +3,10 @@ package fr.alnotz;
 public class Dual implements IsDual{
     private double r;
     private double d;
+    public Dual(){
+        this.r = 0;
+        this.d = 0;
+    }
     public Dual(double r, double d){
         this.r = r;
         this.d = d;
@@ -10,6 +14,15 @@ public class Dual implements IsDual{
     public static Dual plus(IsDual dual0, IsDual dual1){
         return new Dual(dual0.getR() + dual1.getR(), dual0.getD() + dual1.getD());
     }
+    public static Dual times(IsDual dual0, IsDual dual1){
+        return new Dual(dual0.getR() * dual1.getR(), dual0.getR() * dual1.getD() + dual1.getR() * dual0.getD());
+    }
+    public static Dual conjugate(IsDual dual){
+        return new Dual(dual.getR(), -1 * dual.getD());
+    }
+    public static boolean equals(IsDual dual0, IsDual dual1){
+        return dual0.getR() == dual1.getR() && dual0.getD() == dual1.getD();
+    }
     @Override
     public double getR() {
         return this.r;
@@ -35,15 +48,21 @@ public class Dual implements IsDual{
         this.r += dual.getR();
         this.d += dual.getD();
     }
-
     @Override
     public void times(IsDual dual) {
         this.r *= dual.getR();
-        this.d = 2 * this.r * dual.getD();
+        this.d = this.r * dual.getD() + this.d * dual.getR();
+    }
+    @Override
+    public void conjugate(){
+        this.d *= -1;
     }
-
     @Override
     public boolean equals(IsDual dual) {
-        return this.r == dual.getR() && this.d == dual.getR();
+        return this.r == dual.getR() && this.d == dual.getD();
+    }
+    @Override
+    public String toString(){
+        return String.format("%+f %+fε\n", this.r, this.d);
     }
 }
diff --git a/fr/alnotz/IsDual.java b/fr/alnotz/IsDual.java
index 221bd0e..e5ee819 100644
--- a/fr/alnotz/IsDual.java
+++ b/fr/alnotz/IsDual.java
@@ -7,5 +7,7 @@ public interface IsDual {
     void setD(double d);
     void plus(IsDual dual);
     void times(IsDual dual);
+    void conjugate();
     boolean equals(IsDual dual);
+    String toString();
 }
diff --git a/fr/alnotz/IsQuaternion.java b/fr/alnotz/IsQuaternion.java
new file mode 100644
index 0000000..4ff97f5
--- /dev/null
+++ b/fr/alnotz/IsQuaternion.java
@@ -0,0 +1,17 @@
+package fr.alnotz;
+
+public interface IsQuaternion {
+    double getS();
+    double getI();
+    double getJ();
+    double getK();
+    void setS();
+    void setI();
+    void setJ();
+    void setK();
+    void plus(IsQuaternion quaternion);
+    void times(IsQuaternion quaternion);
+    void conjugate();
+    boolean equals(IsQuaternion quaternion);
+    String toString();
+}
diff --git a/fr/alnotz/Quaternion.java b/fr/alnotz/Quaternion.java
new file mode 100644
index 0000000..d68d338
--- /dev/null
+++ b/fr/alnotz/Quaternion.java
@@ -0,0 +1,79 @@
+package fr.alnotz;
+
+public class Quaternion implements IsQuaternion{
+    private double s;
+    private double i;
+    private double j;
+    private double k;
+    public Quaternion(){
+        this.s = 0;
+        this.i = 0;
+        this.j = 0;
+        this.k = 0;
+    }
+    public Quaternion(double s, double i, double j, double k){
+        this.s = s;
+        this.i = i;
+        this.j = j;
+        this.k = k;
+    }
+    @Override
+    public double getS() {
+        return 0;
+    }
+
+    @Override
+    public double getI() {
+        return 0;
+    }
+
+    @Override
+    public double getJ() {
+        return 0;
+    }
+
+    @Override
+    public double getK() {
+        return 0;
+    }
+
+    @Override
+    public void setS() {
+
+    }
+
+    @Override
+    public void setI() {
+
+    }
+
+    @Override
+    public void setJ() {
+
+    }
+
+    @Override
+    public void setK() {
+
+    }
+
+    @Override
+    public void plus(IsQuaternion quaternion) {
+
+    }
+
+    @Override
+    public void times(IsQuaternion quaternion) {
+
+    }
+
+    @Override
+    public void conjugate() {
+
+    }
+
+    @Override
+    public boolean equals(IsQuaternion quaternion) {
+        return false;
+    }
+}