code: public synchronized void addObserver(String notification, ApptentiveNotificationObserver observer, boolean useWeakReference) {
  		final ApptentiveNotificationObserverList list = resolveObserverList(notification);
  		list.addObserver(observer, useWeakReference);
  	}
docs: Adds an entry to the receiver’s dispatch table with an observer.
  
  @param useWeakReference - weak reference is used if <code>true</code>