In "Rent Seeking Behind the Green Curtain" by Jonathan H. Adler 1996, Regulation issue 4 pages 26-34, the author mentions a discussion of the 1977 Clean Air Act amendments that required scrubbers rather than allowing the switch to low sulphur coal occur as an endogenous response to coal emissions policy. The article lists the original source for the argument as "Clean coal/dirty air : or how the Clean air act became a multibillion-dollar bail-out for high-sulfur coal producers and what should be done about it", by Bruce A. Ackerman and William T. Hassler New Haven : Yale University Press, c1981.