On of the most common questions I get is how to properly acknowledge the use of a program like SPSS in a research publication. In a series of messages in the MedStats discussion group (August 2006) about the citation of statistical software, one writer (JU) pointed out that a bibliographic citation in a consistent format is important because various sources track the frequency of citations in research.
I have an entry about citing software in my Ask Professor Mean section, and I have updated it to include this observation.