Array ( [0] => Array ( [title] => L2A [link] => https://www.youtube.com/embed/12rUWo5iE44 ) [1] => Array ( [title] => L2B [link] => https://www.youtube.com/embed/XkMQcm_raK8 ) [2] => Array ( [title] => L2C [link] => https://www.youtube.com/embed/WvFoEvNZMWI ) [3] => Array ( [title] => L2D [link] => https://www.youtube.com/embed/3uhUQvPUgTM ) ) 國立清華大學開放式課程OpenCourseWare(NTHU, OCW) - 第2R講 2.1 Theorems of Open Sets