While an annual subscription allows purchasing CDs and audiotapes for 33% less than individually-ordered recordings, why not take advantage of 50% savings and purchase your lectures as mp3 audio files downloaded from this website.  All recorded lectures from 1981 through 2012 are now available in all three formats.  However, using the mp3 download option helps to save precious resources, including your money and our time!  Thank you for your interest and support that will help to ensure the availability of thought provoking presentations in the future.