Selder Dennis J, Roll G Frederick, Carter J E Lindsay
Phys Sportsmed. 1980 Sep;8(9):101-105. doi: 10.1080/00913847.1980.11948638.
These upper middle-class senior citizens play tennis to stay healthy and to enjoy life, but their experience doesn't necessarily apply to the rest of society.
这些中上层阶级的老年人打网球是为了保持健康和享受生活，但他们的经历并不一定适用于社会其他群体。
