tourism 的定义，从what,who,when三方面来讲述。

why is it difficult to define the tourism?  five points.

modern tourism causes: four points

modern tourism effects: three points

significance in 1991 international conference on travel and tourism statistics convened by WTO :  three points

tourism define by WTO: what? who? where? how long? what purpose?从五个方面讲tourism定义

categories of tourism:1.international tourism 2. internal tourism .3.domestic tourism. 4.national tourism.