Bensman, Stephen J. (2000) Probability distributions in library and information science: a historical and practitioner viewpoint . Journal of the American Society for Information Science, 51, (9), 816-833
2.
Hafner, A.W. (1998) Descriptive statistical techniques for librarians. 2nd ed.Chicago: ALA
3.
Stephen, Peter and Hornby, Susan (1997) Simple statistics for library and information professionals. 2nd ed.London: Library Association Publishing