Sales of Pink Floyd's 1973 classic album Dark Side of the Moon show little sign of calming down, some 35 years after release. Although it has slipped recently to the high 20's in the Billboard Catalog chart, DSOTM recently eclipsed 31 years on the Pop & Catalog charts. Last week it had reached a staggering 1,615 weeks on the charts. Our thanks to Bill Dorn for this interesting statistic...