That is written in the The iMums Website:
Fast Free and Discounted Apps! July 21
These Free and Discounted Apps are on sale for a limited time only so you’ll need to be Fast if you want them at the reduced price. These apps were free or discounted at the time of publishing this article but are subject to change at any time by the app developers.
History Lines by Alireza Montazery
Read more on: The iMums