编辑同志：您好！我是一名游泳爱好者，不但非常热爱游泳这项运动，而且还收集“游泳”专题邮票，并有组集参展的愿望。我今天要请教的问题是：游泳项目（仰、蛙、蝶、自）是在哪年、哪届、哪个国家举行的奥运会上成为正式比赛项目的？这些比赛项目具体是什么？成绩如何？... Edit comrades: Hello! I am a swimming enthusiast. I not only love swimming very much, but also collect “swimming” special stamps and have the desire to organize exhibitions. My question today to ask is: swimming project (Yang, frogs, butterflies, from) is in which year, which session, which country Olympic Games to become a formal event? What are these competitions specifically? What’s the grade? ...