Anytime the phrase Certified Hits is used in conjunction with an artist anthology, it usually means that the product before you is a "Cliffs Notes" overview that belongs with the George Jones and Willie Nelson versions behind the plastic, "Slim Jim" sponsored kiosk at your local truck stop. The Nitty Gritty Dirt Band has released more than 20 records in their constantly evolving career and still compilers insist on regurgitating the exact same songs for every bargain-bin retrospective. While "Mr. Bojangles," "An American Dream," and "Ripplin' Waters" are indeed classics, the hundreds of songs left behind must surely be contemplating a mass exodus from the industry.