medical marijuana profits The importance of gasoline was not recognized in the 19th century, when it was used in a great deal of kerosene. The oil refining then relied on simple distillation processes to separate the different components of the oil from the boiling point. The boiling point of the kerosene component is higher, and the use of safety when lighting lamps becomes the main product of crude oil refining, while gasoline and other components are often burned as fuel. By the mid - to late 19th century, the successful use of gasoline engines in 1886, in 1886, the gasoline engine was successfully used as a driving force, thus the importance of gasoline increased. But using distillation, only 20% of the gasoline can be extracted from crude oil. In 1911, the standard oil company have solved the problem of low gasoline yield, by William burton and Robert hamm forest thermal cracking process of the invention, the heavy quality heating gas oil cracking of light gasoline fractions, such as to overall improve the gasoline yield, thermal cracking process in 1913 won the patent license in the United States. The subsequent catalytic cracking process has further improved the gasoline yield and octane value. Commercial vehicles: vehicles used for transporting personnel and goods in design and technical features, and can be tractor-trailer. Passenger cars are not included. Commercial vehicles are divided into three categories: passenger cars, vans and semi-trailer tractors. The passenger bus subdivided into small passenger car, city bus, coach, tourist bus, articulated bus, coach, cross-country coach and private bus. Goods vehicles are subdivided into general goods vehicles, multi-purpose lorries, full trailer tractors, off-road trucks, special operations vehicles and special goods vehicles. Lay the foundation previously warned: "positions are too crowded to cause some pain."