1. Introduction
Information and Communication Technology (ICT) have been reshaping nearly every corner of the world, especially the way of people's communication. Today, our knowledge can be easily collected, stored, and distributed digitally. Researchers have been using new communication tools to facilitate the exchange of information. However, these document (text) data have grown exponentially in recent decades, and numerous research articles are created, digitized, and stored in various research databases. It is almost impossible for a researcher to do thoroughly literature search and review on a tremendous number of articles in order to understand recent progress of his/her research of interest. Many research databases, scholarly search engines, and citation recommendation systems have been created to help tackle this problem. To gather literature related to a research is much easier today, but we are still facing challenges to determine whether a research topic (or just a term) is rarely explored by others, just emerging from discussions of small groups, or potentially connected to topics in other fields of studies-problems of topic diffusion discovery.