I thought the attached article might be interesting to folks. Jud --- Dr. Judson L. Ahern Professor Emeritus, Geophysics School of Geology & Geophysics University of Oklahoma Norman, OK 73019 [log in to unmask] W5JA ######################################################################## To unsubscribe from the CUBA-L list, click the following link: &*TICKET_URL(CUBA-L,SIGNOFF);