Maurizio Pietrantuono thinks this is interesting: At this point, we replace completion notification with another Observable<Rating>. S From 3. Operators and Transformations from Reactive Programming with RxJava by Ben Christensen, Tomasz Nurkiewicz Publisher: O'Reilly Media, Inc. Released: October 2016 Note nice!!! Share this highlight http://learning.oreilly.com/a/reactive-programming-with/11078131/ Twitter Facebook Google Plus Email Get Instant Access Now Start a Free Trial Have an account? Sign in.