Abstract
Although collaboration in reference has been speculated to have numerous benefits, studies of collaboration in libraries have primarily focused on collaboration at the institutional level. This article describes the development of a typology of collaborative communication between volunteer reference librarians in an e-mail-based digital reference service, ipl2's Ask an ipl2 Librarian. Researchers examined the transcripts of 574 e-mail reference transactions that contained at least one instance of collaborative communication. The resulting analysis uncovered four types of collaborative communication: content, service, technology, and community. These findings have implications for the practice of digital reference and the design of digital reference systems.