diff --git a/arraylist/ArrayIndexList.java b/arraylist/ArrayIndexList.java
index fa55fff..0b83aa8 100644
--- a/arraylist/ArrayIndexList.java
+++ b/arraylist/ArrayIndexList.java
@@ -6,6 +6,8 @@ package arraylist;
  * Date: 24/03/14
  * Time: 14:31
  */
+//Copyright (c) 2003 Brown University, Providence, RI
+//Additional modifications and methods by xgiovio
 
     public class ArrayIndexList<E> implements IndexList<E> {
         private E[] array;
diff --git a/arraylist/IndexList.java b/arraylist/IndexList.java
index 247c9ec..bf08f34 100644
--- a/arraylist/IndexList.java
+++ b/arraylist/IndexList.java
@@ -6,6 +6,8 @@ package arraylist;
  * Date: 24/03/14
  * Time: 14:29
  */
+//Copyright (c) 2003 Brown University, Providence, RI
+//Additional modifications and methods by xgiovio
 public interface IndexList<E> {
 
 
diff --git a/com/xgiovio/NodePositionListTest.java b/com/xgiovio/NodePositionListTest.java
new file mode 100644
index 0000000..8069bcb
--- /dev/null
+++ b/com/xgiovio/NodePositionListTest.java
@@ -0,0 +1,35 @@
+package com.xgiovio;
+
+import arraylist.ArrayIndexList;
+import general_utility.test_object;
+import position.NodePositionList;
+
+/**
+ * Created with xgiovio.macbookair.
+ * User: xgiovio
+ * Date: 23/03/14
+ * Time: 20:37
+ */
+public class NodePositionListTest {
+
+    public static void main(String[] args) {
+        NodePositionList<test_object> a = new NodePositionList<test_object>();
+
+        a.addLast(new test_object(1));
+        a.addLast(new test_object(2));
+        a.addLast(new test_object(3));
+        a.addLast(new test_object(4));
+
+
+        System.out.print(a);
+        a.reverse();
+        System.out.print(a);
+
+
+
+
+
+
+    }
+
+}
diff --git a/deque/Deque.java b/deque/Deque.java
index 931a499..7978192 100644
--- a/deque/Deque.java
+++ b/deque/Deque.java
@@ -8,6 +8,8 @@ import exceptions.EmptyDequeException;
  * Date: 17/03/14
  * Time: 16:21
  */
+//Copyright (c) 2003 Brown University, Providence, RI
+//Additional modifications and methods by xgiovio
 public interface Deque<E> {
 
     int size();
diff --git a/deque/NodeDeque.java b/deque/NodeDeque.java
index 8715f04..28a01e3 100644
--- a/deque/NodeDeque.java
+++ b/deque/NodeDeque.java
@@ -9,6 +9,8 @@ import exceptions.EmptyDequeException;
  * Date: 17/03/14
  * Time: 16:26
  */
+//Copyright (c) 2003 Brown University, Providence, RI
+//Additional modifications and methods by xgiovio
 public class NodeDeque<E> implements Deque <E>  {
 
     public NodeDeque(){
diff --git a/deque/utility/DLNode.java b/deque/utility/DLNode.java
index 34ad38a..94cb2b7 100644
--- a/deque/utility/DLNode.java
+++ b/deque/utility/DLNode.java
@@ -6,6 +6,9 @@ package deque.utility;
  * Date: 17/03/14
  * Time: 16:32
  */
+
+//Copyright (c) 2003 Brown University, Providence, RI
+//Additional modifications and methods by xgiovio
 public class DLNode <E> {
 
     public DLNode (){
diff --git a/exceptions/BoundaryViolationException.java b/exceptions/BoundaryViolationException.java
new file mode 100644
index 0000000..ab93c0a
--- /dev/null
+++ b/exceptions/BoundaryViolationException.java
@@ -0,0 +1,18 @@
+package exceptions;
+
+/**
+ * Signals that the boundaries of a data structure have been illegally
+ * traversed (e.g. past the end of a list).
+ * @author Roberto Tamassia
+ */
+//Copyright (c) 2003 Brown University, Providence, RI
+//Additional modifications and methods by xgiovio
+
+public class BoundaryViolationException extends RuntimeException {
+  public BoundaryViolationException(String message) {
+    super (message);
+  }
+    public BoundaryViolationException() {
+        super ("BoundaryViolationException");
+    }
+}
diff --git a/exceptions/EmptyListException.java b/exceptions/EmptyListException.java
new file mode 100644
index 0000000..43a16ea
--- /dev/null
+++ b/exceptions/EmptyListException.java
@@ -0,0 +1,18 @@
+package exceptions;
+/**
+ * Thrown when a list cannot fulfill the requested operation because
+ * it is empty.
+ * @author Roberto Tamassia
+ */
+//Copyright (c) 2003 Brown University, Providence, RI
+//Additional modifications and methods by xgiovio
+
+
+public class EmptyListException extends RuntimeException {
+  public EmptyListException(String message) {
+    super (message);
+  }
+    public EmptyListException() {
+        super ("EmptyListException");
+    }
+}
diff --git a/exceptions/InvalidPositionException.java b/exceptions/InvalidPositionException.java
new file mode 100644
index 0000000..2cebd38
--- /dev/null
+++ b/exceptions/InvalidPositionException.java
@@ -0,0 +1,21 @@
+package exceptions;
+/**
+ * Thrown when a position is determined to be invalid.
+ * @author Roberto Tamassia, Michael Goodrich
+ */
+//Copyright (c) 2003 Brown University, Providence, RI
+//Additional modifications and methods by xgiovio
+
+
+public class InvalidPositionException extends RuntimeException {  
+  public InvalidPositionException(String err) {
+    super(err);
+  }
+
+  public InvalidPositionException() {
+      super("Invalid Position");
+
+  }
+
+}
+
diff --git a/position/DNode.java b/position/DNode.java
new file mode 100644
index 0000000..5f8695e
--- /dev/null
+++ b/position/DNode.java
@@ -0,0 +1,36 @@
+package position;
+import  exceptions.*;
+/**
+ * A simple node class for a doubly-linked list.  Each DNode has a
+ * reference to a stored element, a previous node, and a next node.
+ * 
+ * @author Roberto Tamassia
+ */
+//Copyright (c) 2003 Brown University, Providence, RI
+//Additional modifications and methods by xgiovio
+
+public class DNode<E> implements Position<E> {
+  private DNode<E> prev = null;
+    private DNode<E> next = null;
+  private E element = null;
+
+  public DNode(DNode<E> newPrev, DNode<E> newNext, E elem) {
+    prev = newPrev;
+    next = newNext;
+    element = elem;
+  }
+
+  public E element() throws InvalidPositionException {
+    if ((prev == null) && (next == null))
+      throw new InvalidPositionException("Position is not in a list!");
+    return element;
+  }
+
+  public DNode<E> getNext() { return next; }
+  public DNode<E> getPrev() { return prev; }
+
+  public void setNext(DNode<E> newNext) { next = newNext; }
+  public void setPrev(DNode<E> newPrev) { prev = newPrev; }
+  public void setElement(E newElement) { element = newElement; }
+}
+
diff --git a/position/NodePositionList.java b/position/NodePositionList.java
new file mode 100644
index 0000000..fce1dcb
--- /dev/null
+++ b/position/NodePositionList.java
@@ -0,0 +1,190 @@
+package position;
+import java.util.Iterator;
+import  exceptions.*;
+import stack.utility.Node;
+
+/**
+ * Realization of a PositionList using a doubly-linked list of nodes.
+ *   
+ * @author Michael Goodrich, Natasha Gelfand, Roberto Tamassia, Eric Zamore
+ */
+//Copyright (c) 2003 Brown University, Providence, RI
+//Additional modifications and methods by xgiovio
+
+public class NodePositionList<E> implements PositionList<E> {
+
+  protected int numElts;            	// Number of elements in the list
+  protected DNode<E> header, trailer;	// Special sentinels
+
+  public NodePositionList() {
+    numElts = 0;
+    header = new DNode<E>(null, null, null);	// create header
+    trailer = new DNode<E>(header, null, null);	// create trailer
+    header.setNext(trailer);	// make header and trailer point to each other
+  }
+
+  protected DNode<E> checkPosition(Position<E> p)  throws InvalidPositionException {
+    if (p == null)
+      throw new InvalidPositionException
+	("Null position passed to NodeList");
+    if (p == header)
+	throw new InvalidPositionException
+	  ("The header node is not a valid position");
+    if (p == trailer)
+	throw new InvalidPositionException
+	  ("The trailer node is not a valid position");
+    try {
+      DNode<E> temp = (DNode<E>) p;
+      if ((temp.getPrev() == null) || (temp.getNext() == null))
+	throw new InvalidPositionException
+	  ("Position does not belong to a valid NodeList");
+      return temp;
+    } catch (ClassCastException e) {
+      throw new InvalidPositionException
+	("Position is of wrong type for this list");
+    }
+  }
+
+  public int size() { return numElts; }
+
+  public boolean isEmpty() { return (numElts == 0); }
+
+  public Position<E> first()     throws EmptyListException {
+    if (isEmpty())
+      throw new EmptyListException("List is empty");
+    return header.getNext();
+  }
+
+  public Position<E> last()
+      throws EmptyListException {
+    if (isEmpty())
+      throw new EmptyListException("List is empty");
+    return trailer.getPrev();
+  }
+
+  public Position<E> prev(Position<E> p)        throws InvalidPositionException, BoundaryViolationException {
+    DNode<E> v = checkPosition(p);
+    DNode<E> prev = v.getPrev();
+    if (prev == header)
+      throw new BoundaryViolationException
+	("Cannot advance past the beginning of the list");
+    return prev;
+  }
+
+  public Position<E> next(Position<E> p)   throws InvalidPositionException, BoundaryViolationException {
+    DNode<E> v = checkPosition(p);
+    DNode<E> next = v.getNext();
+    if (next == trailer)
+      throw new BoundaryViolationException
+	("Cannot advance past the end of the list");
+    return next;
+  }
+
+  public void addBefore(Position<E> p, E element)         throws InvalidPositionException {
+    DNode<E> v = checkPosition(p);
+    numElts++;
+    DNode<E> newNode = new DNode<E>(v.getPrev(), v, element);
+    v.getPrev().setNext(newNode);
+    v.setPrev(newNode);
+  }
+
+  public void addAfter(Position<E> p, E element) 
+      throws InvalidPositionException {
+    DNode<E> v = checkPosition(p);
+    numElts++;
+    DNode<E> newNode = new DNode<E>(v, v.getNext(), element);
+    v.getNext().setPrev(newNode);
+    v.setNext(newNode);
+  }
+
+  public void addFirst(E element) {
+    numElts++;
+    DNode<E> newNode = new DNode<E>(header, header.getNext(), element);
+    header.getNext().setPrev(newNode);
+    header.setNext(newNode);
+  }
+
+  public void addLast(E element) {
+    numElts++;
+    DNode<E> oldLast = trailer.getPrev();
+    DNode<E> newNode = new DNode<E>(oldLast, trailer, element);
+    oldLast.setNext(newNode);
+    trailer.setPrev(newNode);
+  }
+
+  public E remove(Position<E> p)
+      throws InvalidPositionException {
+    DNode<E> v = checkPosition(p);
+    numElts--;
+    DNode<E> vPrev = v.getPrev();
+    DNode<E> vNext = v.getNext();
+    vPrev.setNext(vNext);
+    vNext.setPrev(vPrev);
+    E vElem = v.element();
+
+    v.setNext(null);
+    v.setPrev(null);
+    return vElem;
+  }
+
+  public E set(Position<E> p, E element)
+      throws InvalidPositionException {
+    DNode<E> v = checkPosition(p);
+    E oldElt = v.element();
+    v.setElement(element);
+    return oldElt;
+  }
+
+
+
+  public boolean isFirst(Position<E> p)
+    throws InvalidPositionException {  
+    DNode<E> v = checkPosition(p);
+    return v.getPrev() == header;
+  }
+
+  public boolean isLast(Position<E> p)
+      throws InvalidPositionException {  
+    DNode<E> v = checkPosition(p);
+    return v.getNext() == trailer;
+  }
+
+  public void swapElements(Position<E> a, Position<E> b) 
+      throws InvalidPositionException {
+    DNode<E> pA = checkPosition(a);
+    DNode<E> pB = checkPosition(b);
+    E temp = pA.element();
+    pA.setElement(pB.element());
+    pB.setElement(temp);
+  }
+
+
+    @Override
+    public String toString() {
+        String to_return = "";
+        to_return = to_return + "[";
+
+        for (  DNode<E> temp = header.getNext(); temp != trailer ; temp = temp.getNext()){
+
+            if ( temp.getNext() == trailer){
+                to_return+=(temp.element().toString());
+            }else{
+                to_return+=(temp.element().toString() + ",");
+            }
+        }
+        to_return = to_return + "]";
+
+        return to_return;
+    }
+
+
+    public void reverse(){
+          if (size() > 1){
+              E temp = remove(last());
+              reverse();
+              addFirst(temp);
+          }
+    }
+
+
+}
diff --git a/position/Position.java b/position/Position.java
new file mode 100644
index 0000000..8c41538
--- /dev/null
+++ b/position/Position.java
@@ -0,0 +1,14 @@
+package position;
+/**
+ * An interface for a position, which is a holder object storing a
+ * single element.
+ * @author Roberto Tamassia, Michael Goodrich
+ */
+//Copyright (c) 2003 Brown University, Providence, RI
+//Additional modifications and methods by xgiovio
+
+public interface Position<E> {
+
+  E element();
+}
+
diff --git a/position/PositionList.java b/position/PositionList.java
new file mode 100644
index 0000000..0d534d1
--- /dev/null
+++ b/position/PositionList.java
@@ -0,0 +1,40 @@
+package position;
+import java.util.Iterator;
+import  exceptions.*;
+
+/**
+ * An interface for positional lists.
+ * @author Roberto Tamassia, Michael Goodrich
+ */
+//Copyright (c) 2003 Brown University, Providence, RI
+//Additional modifications and methods by xgiovio
+public interface PositionList<E>  {
+
+
+  public int size();
+
+  public boolean isEmpty();
+
+  public Position<E> first();
+
+  public Position<E> last();
+
+  public Position<E> next(Position<E> p)      throws InvalidPositionException, BoundaryViolationException;
+
+  public Position<E> prev(Position<E> p)      throws InvalidPositionException, BoundaryViolationException;
+
+  public void addFirst(E e);
+
+  public void addLast(E e);
+
+  public void addAfter(Position<E> p, E e)         throws InvalidPositionException;
+
+  public void addBefore(Position<E> p, E e)       throws InvalidPositionException;
+
+  public E remove(Position<E> p) throws InvalidPositionException;
+
+  public E set(Position<E> p, E e) throws InvalidPositionException;
+
+
+}
+
diff --git a/queue/ArrayQueue.java b/queue/ArrayQueue.java
index c12a84f..a45c4c3 100644
--- a/queue/ArrayQueue.java
+++ b/queue/ArrayQueue.java
@@ -8,6 +8,8 @@ import exceptions.EmptyQueueException;
  * Date: 10/03/14
  * Time: 15:49
  */
+//Copyright (c) 2003 Brown University, Providence, RI
+//Additional modifications and methods by xgiovio
 public class ArrayQueue<E> implements Queue<E> {
 
       public ArrayQueue(){
diff --git a/queue/NodeQueue.java b/queue/NodeQueue.java
index 993f7f6..db5daed 100644
--- a/queue/NodeQueue.java
+++ b/queue/NodeQueue.java
@@ -11,6 +11,8 @@ import java.awt.image.AreaAveragingScaleFilter;
  * Date: 17/03/14
  * Time: 14:08
  */
+//Copyright (c) 2003 Brown University, Providence, RI
+//Additional modifications and methods by xgiovio
 public class NodeQueue<E> implements Queue<E> {
 
 
diff --git a/queue/Queue.java b/queue/Queue.java
index 916f2f0..6cae156 100644
--- a/queue/Queue.java
+++ b/queue/Queue.java
@@ -8,6 +8,8 @@ import exceptions.EmptyQueueException;
  * Date: 10/03/14
  * Time: 15:45
  */
+//Copyright (c) 2003 Brown University, Providence, RI
+//Additional modifications and methods by xgiovio
  public interface Queue<E> {
 
     public  void enqueue (E element);
diff --git a/stack/ArrayStack.java b/stack/ArrayStack.java
index 8d30ad0..a7ca043 100644
--- a/stack/ArrayStack.java
+++ b/stack/ArrayStack.java
@@ -9,7 +9,8 @@ import exceptions.EmptyStackException;
  * Date: 05/03/14
  * Time: 0.12
  */
-
+//Copyright (c) 2003 Brown University, Providence, RI
+//Additional modifications and methods by xgiovio
 
 public class ArrayStack<E> implements Stack<E> {
 
diff --git a/stack/NodeStack.java b/stack/NodeStack.java
index 16655b8..81a8c3c 100644
--- a/stack/NodeStack.java
+++ b/stack/NodeStack.java
@@ -9,7 +9,8 @@ import stack.utility.Node;
  * Date: 05/03/14
  * Time: 0.12
  */
-
+//Copyright (c) 2003 Brown University, Providence, RI
+//Additional modifications and methods by xgiovio
 
 public class NodeStack<E> implements Stack<E> {