Pop culture writer/filmmaker Steven Blush ("American Hardcore") joins the festivities this week to (at long last) help us delve into the enigmatic story of the original 1970s-era incarnation of World Team Tennis - including an exclusive preview of his upcoming book & documentary Bustin' Balls: World Team Tennis - Pro Sports, Pop Culture and Progressive Politics.   From the "Bustin' Balls" book dust jacket:   "Tennis. Exquisitely tailored white outfits. Formally attired spectators.  Stiff upper lips and utterly antiquated attitudes that made the sport accessible only to wealthy WASPs.   "'Tennis is the perfect combination of violent action taking place in an atmosphere of total tranquility,' said legendary rule-breaker Billie Jean King in 1973.   "By 1974, Ms. King and a group of investors made up of fans, promoters, and at least one used-car salesman crashed the country clubs and well-manicured courts with the creation of World Team Tennis - and eliminated proper etiquette in tennis forever.   "Tennis stars from the far reaches of the world came to Cleveland, Philadelphia and Los Angeles, and showed a new breed of fans that the emotional passion and physical violence on the court were as entertaining as any Sunday afternoon football.  Between cursing out judges, encouraging personal grudges, and the "anything goes" milieu of the 70s, World Team Tennis busted through all race, sex and gender barriers.   "Bustin' Balls is the entirely true story of the most controversial, influential and fantastic sports league you never heard of."