diff --git a/docs/lecture 20/Lecture20_part1.pdf b/docs/lecture 20/Lecture20_part1.pdf new file mode 100644 index 0000000000000000000000000000000000000000..609bc7647cfda16619c281279ebd24c8f512185e Binary files /dev/null and b/docs/lecture 20/Lecture20_part1.pdf differ diff --git a/docs/lecture 20/note.md b/docs/lecture 20/note.md deleted file mode 100644 index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..0000000000000000000000000000000000000000