2[1]Michael McClennen, Patricia Memmott. Roles in Digital Refer ence. Information Technology & Libraries, 20(3)
3[2]Carol Tenopir. Virtual Reference Services in a Real World.Library Journal, 126(12)
4[3]Joseph Janes, David Carter, Patricia Memmott. Digital Reference Services in Academic Libraries. Reference & User Services Quarterly, 39(2)
524/7 Reference Project.(http:www.247ref.org/)
6Real-Time Reference for Undergraduates in Science.Mathematics,and Engineering.(http://www.library.cmu.edu/Libraries/24x7.pdf).
7Ask A Lbrarian.(http://www.earl.org.uk/ask/)
8Collaborative Digital Reference Service.(http://lcweb.loc.gov/rr/digiref/)
9D. N. Kresh, Offering High Quality Reference Service on the Web. D-Lib Magazine6(6) ,June 2000. (http://www.dlib.org/dlib/june 00/kresh/06kresh. html)
