Abstract: The prices of airline tickets between fixed points are in general set by a number of cost parameters, including both fixed costs and operating costs, as well as market conditions, which together are difficult to predict. Among operating costs, there are fuel expenditure on various routes, labor costs, and other administrative expenses, including access charges for gates and airports. Fixed costs include aircraft and their financing. Combined with these highly uncertain cost parameters, reflecting the complexity of the business itself, the prices which airlines ultimately set are effected by market conditions including the changing popularity of various routes, seasonal demand and advertising, and competition between various airlines providing services on these and related routes.

Abstract: A tennis racket has a head having head strings passing through string holes and lieing substantially in a single plane. There is a groove running along a portion of the outside periphery of the head. A flexible member is slidably received in the groove. This member has string apertures therethrough which can register or substantially register with the string holes in the head and the head strings are strung through the said string apertures as well as the string holes. In the throat of the racket there is a tensioning device comprising at least one pinion having a toothed periphery which threadedly engages with teeth on the end portion of the flexible member. By rotating the pinion the flexible member will be moved so as to vary the tension of the strings. A pawl prevents unwanted return movement of the pinion.