Array ( [0] => Array ( [title] => L20A [link] => https://www.youtube.com/embed/qP-CKSon86c ) [1] => Array ( [title] => L20B [link] => https://www.youtube.com/embed/OyxjbIZojR8 ) [2] => Array ( [title] => L20C [link] => https://www.youtube.com/embed/CUZuSPSSS5I ) [3] => Array ( [title] => L20D [link] => https://www.youtube.com/embed/yW1NF1Q-LZA ) ) 國立清華大學開放式課程OpenCourseWare(NTHU, OCW) - 第20講 Prove by Construction R is uncountable