Purpose - The purpose of this paper is to analyze and compare the subject change for both citing and cited literature on digital libraries based on bibliometric techniques. Design/methodology/approach - Library and Information Science Abstracts (LISA) was used to retrieve data of journal articles in digital libraries from 1960 to 2002. By employing the thesaurus search function, three descriptors for subject search, namely electronic library concept, digital libraries and virtual library concept, as suggested by LISA, were used to retrieve all relevant literature on digital libraries. Findings - Most of the citing core journals on digital libraries are devoted to the subject of the application of computer and information technology to library implication, while the cited literature on digital libraries distributes mainly into four types of journals, namely, digital library orientation, general library and information science, new development in librarianship, and library technology. Digital libraries, electronic media and world wide web (WWW) are the three subject terms in common most for both citing and cited core journal literature. They also constitute the core subject for digital library literature. The change of highly used subject terms, such as WWW, internet, library technology, network, university or academic library, from cited to citing literature suggests that these subjects are becoming the main stream of researches in digital libraries. Research limitations/implications - Most subject terms of this study for both citing and cited literature in digital libraries could be categorized into the technical issues. However, other related issues dealing with copyright, charging and authenticity; social issues; quality of preservation and availability; use and user study; economic issues; education and promotion have not been popular research areas yet by 2002. Further studies are needed. Originality/value - The present work is unique in its study of the subject and the results obtained provide significant insights into the evolution of digital libraries by identifying the core journals and examining their characteristics, as well as subject changes between citing and cited literature on digital libraries.
