Recent years have witnessed tremendous developments in the field of information technology
(IT) and a great increase in the pervasiveness of the Internet. With these changes, many
news organizations and broadcasting companies have been ceaselessly producing a huge
amount of news articles and TV programs, respectively. In particular, with the recent
smartphone boom, user-generated content (UGC) has come to constitute a significant
portion of the total volume of digital content. Accordingly, there is a strong and urgent need
to provide or recommend appropriate digital contents to users. Many content recommendation
systems have already been developed for this purpose. In such systems, a frequently
used approach is to select hot or popular contents for recommendation based on some
popularity metric.