public void AddRef(string name, string location)
 {
     if (MathNode.IncludeInReference(name))
     {
         for (int i = 0; i < this.Count; i++)
         {
             if (this[i].Name == name)
             {
                 return;
             }
         }
         this.Add(new AssemblyRef(name, location));
     }
 }