Distribution Research-National Geographic

National Geographic has partnered with multiple software groups to make sure as much digital access to their magazine is available. For Iphones, they have their app on the App Store.
For andriods, the google play store also offers their app.
Besides these apps, they still offer online subscriptions to their issues.

They also have an online library. This means that once people subscribe they gain access to all the recent issues. With their children's library also included within their subscription, national geographic is able to spread as many versions of their magazine around and provide as great of an incentive to users to also use multiple forms of their service.