diff --git a/binarytree/BTNode.java b/binarytree/BTNode.java
new file mode 100644
index 0000000..4fa15be
--- /dev/null
+++ b/binarytree/BTNode.java
@@ -0,0 +1,35 @@
+package binarytree;
+
+public class BTNode<E> implements BTPosition<E> {
+
+  private E element = null;
+  private BTPosition<E> left   = null;
+  private BTPosition<E> right = null;
+  private BTPosition<E> parent = null;
+
+  public BTNode() { }
+
+
+  public BTNode(E element, BTPosition<E> parent, BTPosition<E> left, BTPosition<E> right) {
+    setElement(element);
+    setParent(parent);
+    setLeft(left);
+    setRight(right);
+  }
+
+  public E element() { return element; }
+
+  public void setElement(E o) { element=o; }
+
+  public BTPosition<E> getLeft() { return left; }
+
+  public void setLeft(BTPosition<E> v) { left=v; }
+
+  public BTPosition<E> getRight() { return right; }
+
+  public void setRight(BTPosition<E> v) { right=v; }
+
+  public BTPosition<E> getParent() { return parent; }
+
+  public void setParent(BTPosition<E> v) { parent=v; }
+}
diff --git a/binarytree/BTPosition.java b/binarytree/BTPosition.java
new file mode 100644
index 0000000..a951bfe
--- /dev/null
+++ b/binarytree/BTPosition.java
@@ -0,0 +1,14 @@
+package binarytree;
+
+
+import position.Position;
+
+public interface BTPosition<E> extends Position<E> { 	// inherits element()
+  public void setElement(E o);
+  public BTPosition<E> getLeft(); 
+  public void setLeft(BTPosition<E> v); 
+  public BTPosition<E> getRight(); 
+  public void setRight(BTPosition<E> v); 
+  public BTPosition<E> getParent(); 
+  public void setParent(BTPosition<E> v);
+}
diff --git a/binarytree/BinaryTree.java b/binarytree/BinaryTree.java
new file mode 100644
index 0000000..50f7e57
--- /dev/null
+++ b/binarytree/BinaryTree.java
@@ -0,0 +1,20 @@
+package binarytree;
+
+
+import exceptions.BoundaryViolationException;
+import exceptions.InvalidPositionException;
+import position.Position;
+import tree.Tree;
+
+public interface BinaryTree<E> extends Tree<E> {
+
+  public Position<E> left(Position<E> v)       throws InvalidPositionException, BoundaryViolationException;
+
+  public Position<E> right(Position<E> v)       throws InvalidPositionException, BoundaryViolationException;
+
+  public boolean hasLeft(Position<E> v) throws InvalidPositionException;
+
+  public boolean hasRight(Position<E> v) throws InvalidPositionException;
+
+}
+
diff --git a/binarytree/LinkedBinaryTree.java b/binarytree/LinkedBinaryTree.java
new file mode 100644
index 0000000..13e0381
--- /dev/null
+++ b/binarytree/LinkedBinaryTree.java
@@ -0,0 +1,315 @@
+package binarytree;
+import exceptions.BoundaryViolationException;
+import exceptions.EmptyTreeException;
+import exceptions.InvalidPositionException;
+import exceptions.NonEmptyTreeException;
+import position.NodePositionList;
+import position.Position;
+import position.PositionList;
+
+import java.util.Iterator;
+
+
+public class LinkedBinaryTree<E> implements BinaryTree<E> {
+  protected BTPosition<E> root;
+  protected int size;
+
+  public LinkedBinaryTree() { 		    
+    root = null;
+    size = 0;
+  }
+
+
+  public int size() {
+    return size; 
+  } 
+
+  public boolean isEmpty() {
+    return (size == 0); 
+  } 
+
+
+  public boolean isInternal(Position<E> v) throws InvalidPositionException {
+    checkPosition(v);
+    return (hasLeft(v) || hasRight(v));
+  }
+
+  public boolean isExternal(Position<E> v) throws InvalidPositionException {
+    return !isInternal(v);
+  }
+
+  public boolean isRoot(Position<E> v) throws InvalidPositionException { 
+    checkPosition(v);
+    return (v == root()); 
+  }
+
+  public boolean hasLeft(Position<E> v) throws InvalidPositionException { 
+    BTPosition<E> vv = checkPosition(v);
+    return (vv.getLeft() != null);
+  }
+
+  public boolean hasRight(Position<E> v) throws InvalidPositionException { 
+    BTPosition<E> vv = checkPosition(v);
+    return (vv.getRight() != null);
+  }
+
+
+  public Position<E> root() throws EmptyTreeException {
+    if (root == null)
+      throw new EmptyTreeException("The tree is empty");
+    return root;
+  }
+
+
+  public Position<E> left(Position<E> v)     throws InvalidPositionException, BoundaryViolationException {
+    BTPosition<E> vv = checkPosition(v);
+    Position<E> leftPos = vv.getLeft();
+    if (leftPos == null)
+      throw new BoundaryViolationException("No left child");
+    return leftPos;
+  }
+
+
+  public Position<E> right(Position<E> v) 
+    throws InvalidPositionException, BoundaryViolationException { 
+    BTPosition<E> vv = checkPosition(v);
+    Position<E> rightPos = vv.getRight();
+    if (rightPos == null)
+      throw new BoundaryViolationException("No right child");
+    return rightPos;
+   }
+
+
+  public Position<E> parent(Position<E> v)  throws InvalidPositionException, BoundaryViolationException {
+    BTPosition<E> vv = checkPosition(v);
+    Position<E> parentPos = vv.getParent();
+    if (parentPos == null)
+      throw new BoundaryViolationException("No parent");
+    return parentPos; 
+  }
+
+
+  public Iterable<Position<E>> children(Position<E> v)   throws InvalidPositionException {
+   PositionList<Position<E>> children = new NodePositionList<Position<E>>();
+    if (hasLeft(v))
+      children.addLast(left(v));
+    if (hasRight(v))
+      children.addLast(right(v));
+    return children;
+  }
+
+  public Iterable<Position<E>> positions() {
+   PositionList<Position<E>> positions = new NodePositionList<Position<E>>();
+    if(size != 0)
+      preorderPositions(root(), positions);
+    return positions;
+  } 
+
+  public Iterator<E> iterator() {
+    Iterable<Position<E>> positions = positions();
+   PositionList<E> elements = new NodePositionList<E>();
+   for (Position<E> pos: positions) 
+     elements.addLast(pos.element());
+    return elements.iterator();
+  }
+
+  public E replace(Position<E> v, E o)   throws InvalidPositionException {
+    BTPosition<E> vv = checkPosition(v);
+    E temp = v.element();
+    vv.setElement(o);
+    return temp;
+  }
+
+
+  public Position<E> sibling(Position<E> v)  throws InvalidPositionException, BoundaryViolationException {
+      BTPosition<E> vv = checkPosition(v);
+      BTPosition<E> parentPos = vv.getParent();
+      if (parentPos != null) {
+	    BTPosition<E> sibPos;
+	    BTPosition<E> leftPos = parentPos.getLeft();
+	    if (leftPos == vv)
+	        sibPos = parentPos.getRight();
+	    else
+	        sibPos = parentPos.getLeft();
+	    if (sibPos != null)
+	        return sibPos;
+      }
+      throw new BoundaryViolationException("No sibling");
+  }
+
+
+  public Position<E> addRoot(E e) throws NonEmptyTreeException {
+    if(!isEmpty())
+      throw new NonEmptyTreeException("Tree already has a root");
+    size = 1;
+    root = createNode(e,null,null,null);
+    return root;
+  }
+
+
+  public Position<E>  insertLeft(Position<E> v, E e) throws InvalidPositionException {
+    BTPosition<E> vv = checkPosition(v);
+    Position<E> leftPos = vv.getLeft();
+    if (leftPos != null)
+      throw new InvalidPositionException("Node already has a left child");
+    BTPosition<E> ww = createNode(e, vv, null, null);
+    vv.setLeft(ww);
+    size++;
+    return ww;
+  }
+
+  public Position<E>  insertRight(Position<E> v, E e)    throws InvalidPositionException {
+    BTPosition<E> vv = checkPosition(v);
+    Position<E> rightPos = vv.getRight();
+    if (rightPos != null)
+      throw new InvalidPositionException("Node already has a right child");
+    BTPosition<E> w = createNode(e, vv, null, null);
+    vv.setRight(w);
+    size++;
+    return w;
+  }
+
+  public E remove(Position<E> v)  throws InvalidPositionException {
+    BTPosition<E> vv = checkPosition(v);
+    BTPosition<E> leftPos = vv.getLeft();
+    BTPosition<E> rightPos = vv.getRight();
+    if (leftPos != null && rightPos != null)
+      throw new InvalidPositionException("Cannot remove node with two children");
+    BTPosition<E> ww;
+    if (leftPos != null)
+      ww = leftPos;
+    else if (rightPos != null)
+      ww = rightPos;
+    else
+      ww = null;
+    if (vv == root) {
+      if (ww != null)
+	    ww.setParent(null);
+      root = ww;
+    }
+    else {
+      BTPosition<E> uu = vv.getParent();
+      if (vv == uu.getLeft())
+	    uu.setLeft(ww);
+      else
+	    uu.setRight(ww);
+      if(ww != null)
+	    ww.setParent(uu);
+    }
+    size--;
+    return v.element();
+  }
+
+
+  /** Attaches two trees to be subtrees of an external node. */
+  public void attach(Position<E> v, BinaryTree<E> T1, BinaryTree<E> T2)    throws InvalidPositionException {
+    BTPosition<E> vv = checkPosition(v);
+    if (isInternal(v))
+      throw new InvalidPositionException("Cannot attach from internal node");
+    int newSize = size + T1.size() + T2.size();
+    if (!T1.isEmpty()) {
+      BTPosition<E> r1 = checkPosition(T1.root());
+      vv.setLeft(r1);
+      r1.setParent(vv);
+    }
+    if (!T2.isEmpty()) {
+      BTPosition<E> r2 = checkPosition(T2.root());
+      vv.setRight(r2);
+      r2.setParent(vv);
+    }
+    size = newSize;
+  }
+
+  public void swapElements(Position<E> v, Position<E> w)    throws InvalidPositionException {
+    BTPosition<E> vv = checkPosition(v);
+    BTPosition<E> ww = checkPosition(w);
+    E temp = w.element();
+    ww.setElement(v.element());
+    vv.setElement(temp);	
+  }
+
+  public void expandExternal(Position<E> v, E l, E r)     throws InvalidPositionException {
+      checkPosition(v);
+      if (!isExternal(v))
+        throw new InvalidPositionException("Node is not external");
+    insertLeft(v, l);
+    insertRight(v, r);
+  }
+
+  public void removeAboveExternal(Position<E> v)    throws InvalidPositionException {
+      checkPosition(v);
+      if (!isExternal(v))
+        throw new InvalidPositionException("Node is not external");
+    if (isRoot(v))
+      remove(v);
+    else {
+      Position<E> u = parent(v);
+      remove(v);
+      remove(u);
+    }
+  }
+
+
+    public void attachLeaves (PositionList<E> L) {
+           if (!isEmpty())
+               attachLeaves_r(root(),L);
+    }
+
+
+
+    protected void attachLeaves_r(Position<E> v, PositionList<E> L)    throws InvalidPositionException {
+        BTPosition<E>vv = checkPosition(v);
+
+
+        if (hasLeft(v))
+            attachLeaves_r(left(v), L);
+        if (hasRight(v))
+            attachLeaves_r(right(v), L);
+
+        if (isExternal(v)){
+            BTPosition<E> a = createNode(  L.remove(L.first()) ,vv,null,null);
+            BTPosition<E> b = createNode(  L.remove(L.first()) ,vv,null,null);
+            vv.setLeft(a);
+            vv.setRight(b);
+            size+=2;
+        }
+
+    }
+
+
+  // Other methods
+
+  protected BTPosition<E> checkPosition(Position<E> v)     throws InvalidPositionException {
+    if (v == null || !(v instanceof BTPosition) || isEmpty() )
+      throw new InvalidPositionException("The position is invalid");
+    return (BTPosition<E>) v;
+  }
+
+  protected BTPosition<E> createNode(E element, BTPosition<E> parent, BTPosition<E> left, BTPosition<E> right) {
+    return new BTNode<E>(element,parent,left,right); }
+
+
+
+  protected void preorderPositions(Position<E> v, PositionList<Position<E>> pos)    throws InvalidPositionException {
+    pos.addLast(v);
+    if (hasLeft(v))
+      preorderPositions(left(v), pos);
+    if (hasRight(v))
+      preorderPositions(right(v), pos);
+  }
+
+
+  protected void inorderPositions(Position<E> v, PositionList<Position<E>> pos)    throws InvalidPositionException {
+    if (hasLeft(v))
+      inorderPositions(left(v), pos);
+    pos.addLast(v);
+    if (hasRight(v))
+      inorderPositions(right(v), pos);
+  }
+
+
+    @Override
+    public String toString() {
+        return super.toString();
+    }
+}
diff --git a/com/xgiovio/LinkedTreeTest.java b/com/xgiovio/LinkedTreeTest.java
index 63ec56b..2ae543d 100644
--- a/com/xgiovio/LinkedTreeTest.java
+++ b/com/xgiovio/LinkedTreeTest.java
@@ -30,13 +30,14 @@ public class LinkedTreeTest {
         System.out.println(a.isEmpty());
         System.out.println(a);
 
-        a.addChild(100,a.children(a.root()).iterator().next());
+
+        System.out.println(a.height());
+
+        a.remove(a.children(a.root()).iterator().next());
         System.out.println(a.size());
         System.out.println(a.isEmpty());
         System.out.println(a);
 
-        System.out.println(a.height());
-
 
 
 
diff --git a/tree/LinkedTree.java b/tree/LinkedTree.java
index 6a14524..0608ca0 100644
--- a/tree/LinkedTree.java
+++ b/tree/LinkedTree.java
@@ -173,6 +173,31 @@ public class LinkedTree <E> implements Tree<E> {
 
     }
 
+
+
+    public E remove (Position<E> v) {
+        TreePosition<E> a = checkPosition(v);
+        if (isInternal(a))
+            throw new InvalidPositionException();
+        if (size() == 1)
+            return removeRoot();
+
+        PositionList<Position<E>> list = a.getParent().getChildren();
+        Iterable<Position<Position<E>>> it = list.positions();
+
+        for (Position<Position<E>> w : it){
+            if (w.element() == v){
+                size--;
+                return (list.remove(w)).element();
+            }
+        }
+
+        return null;
+    }
+
+
+
+
     public int depth ( Position<E> v) throws InvalidPositionException{
         TreePosition<E> a = checkPosition(v);
         if (a.getParent() == null)