code: public static Object register( Object source, String propertyName, PropertyChangedHandler handler )
  	{
  		return propertyChanges.register(source, propertyName, handler);
  	}
docs: Registers an handler for a specific property change on an object. The object
  itself does not need to implement anything. But at least it should call the
  {@link notify(Object, String)} method when its internal property changes.
  
  @param source The object from which one wants notifications
  @param propertyName The property subscribed. You can use "*" to subscribe to all properties in one time
  @param handler
  @return