Restricting access to Internet content via a paid subscription is often called a paywall. Partial information such as an abstract of content may be available free of charge. Paywalls that allow minimal to no access to content without subscription could be called "hard"; those that allow more flexibility in what users can view without subscribing, such as selective free content, or a limited number of articles per month, or the sampling of several pages of a book or paragraphs of an article are "soft" paywalls. Newspapers started implementing paywalls on their websites in the mid-2010s to increase their revenue, which had been diminishing due to a decline in paid print readership and advertising revenue. Academic papers are often subject to a paywall, and available typically to researchers