Array ( [0] => Array ( [title] => L18A [link] => https://www.youtube.com/embed/EPkjZj60-ug\ ) ) 國立清華大學開放式課程OpenCourseWare(NTHU, OCW) - 第18講|Lecture 3 Special Techniques|3_3B Separation of Variables 3_3_1 Completeness and Orthogonality