In this [page](http://xgrommx.github.io/rx-book/content/getting_started_with_rxjs/creating_and_querying_observable_sequences/backpressure.html), there is a `throttleFirst` method,but the link is 404. Should it be the [throttle](https://github.com/Reactive-Extensions/RxJS/blob/master/doc/api/core/operators/throttle.md) method? 
In this page,
there is a
throttleFirstmethod,but the link is 404. Should it be the throttle method?