Array ( [0] => Array ( [title] => L23A [link] => https://www.youtube.com/embed/EmcxNHupQoE ) [1] => Array ( [title] => L23B [link] => https://www.youtube.com/embed/Q0-rsBqAHdc ) ) 國立清華大學開放式課程OpenCourseWare(NTHU, OCW) - Lecture 23 | Variation-of-constant formula for linear discrete DDEs