code: private Object readResolve() throws ObjectStreamException
  	{
  		LexLocation existing = uniqueLocations.get(this);
  
  		if (existing == null)
  		{
  			return this;
  		} else
  		{
  			return existing;
  		}
  	}
docs: Method to resolve existing locations during de-serialise - as used during deep copy. This is to avoid problems
  with coverage.