41.   But for the city and its suburbs, clean air, good health care, low property taxes and cultural institutions helped tip the scale.

42.   But Coxe still clings to the electric car as a viable option and the California clean air rules.

43.   But if it proves successful, the device will help government regulators enforce clean air laws.

44.   But if Texas fails to comply with federal clean air requirements in the Beaumont, Houston and Dallas areas, some of that federal funding could be in jeopardy.

45.   But our car was fast as long as it had clean air.

46.   But so was a small rally demanding clean air, another involving a local land dispute and another promoting breast-feeding.

47.   But state officials said the relatively clean air recently is largely the result of cool weather.

48.   But the clean air law always contained provisions requiring power companies to seek a permit and install better pollution controls if they substantially upgraded these aging plants.

49.   But they accept that so they can enjoy clean air, clean water, and a safe small-town atmosphere.

50.   But with the passage of clean air laws, the lichens returned, the pale form regained its camouflage, and the black form reverted to rarity.