  /**
   *  Materializes the implicit notifications of an observable sequence as explicit notification values.
   * @returns {Observable} An observable sequence containing the materialized notification values from the source sequence.
   */    
  observableProto.materialize = function () {
    var source = this;
    return new AnonymousObservable(function (observer) {
      return source.subscribe(function (value) {
        observer.onNext(notificationCreateOnNext(value));
      }, function (e) {
        observer.onNext(notificationCreateOnError(e));
        observer.onCompleted();
      }, function () {
        observer.onNext(notificationCreateOnCompleted());
        observer.onCompleted();
      });
    });
  };
