Motorbooks has introduced a pair of style-specific truck books, "The Evolution of Cab-Over-Engine Trucks," by Norm Mort and Doug Grieve, and "Peterbilt Trucks of the 1960s," by Ron Adams. Cab-overs became popular as a way around state length limits, and Mort and Grieve's book covers earlier models in more detail, and those from the 1980s onward more briefly. Peterbilt was well on its way by the 1960s, and was so popular the company had to build a plant in Tennessee to complement Northwest production.