Monthly or yearly membership subscriptions and initial registration fees may apply. It allows subscribers to listen to an unlimited number of songs on-demand through subscriptions. Still others rely solely on paid membership subscriptions. Last.fm Ltd is funded from the sale of online advertising space and monthly user subscriptions. Other approaches to revenue include donations, paid subscriptions and microtransactions. Postcards are also used by magazines for new subscriptions. LexisNexis services are delivered via two websites that require separate paid subscriptions. Rasmussen Reports generates revenue by selling advertising and subscriptions. Xbox Live regulations bar Wargaming from offering premium accounts as recurring subscriptions. Institutions can opt to add Science Classic to their subscriptions for an additional fee. It does not require subscriptions or payment. Worldwide editions are sold on newsstands in addition to regular subscriptions. Before this, Night Mode was only available for users with paid subscriptions. Imgur was profitable at the time, generating revenue from Pro subscriptions and advertising. Open access articles typically are typically cited more often than equivalent articles requiring subscriptions.