B\u00e0i 19: Th\u1ef1c h\u00e0nh: V\u1ebd bi\u1ec3u \u0111\u1ed3 v\u00e0 ph\u00e2n t\u00edch s\u1ef1 ph\u00e2n h\u00f3a v\u1ec1 thu nh\u1eadp b\u00ecnh qu\u00e2n theo \u0111\u1ea7u ng\u01b0\u1eddi gi\u1eefa c\u00e1c v\u00f9ng<\/a><\/blockquote><\/iframe>