links to pre-recorded Lecture 4 videos and slides

README.md

@@ -37,3 +37,4 @@ Note that slides can be found **underneath each lecture video** on switch tube l
 | 2    | Mon | 27.09.2021 | 13:15 | CE1100 | Lecture 3            | [First Symbols. Constructing a Lexer](https://tube.switch.ch/videos/fc864ce0), [Live Recording 1](https://tube.switch.ch/videos/WjS9tOAVex) [From Regular Expressions to Automata](https://tube.switch.ch/videos/a15b1c5f), [Live Recording 2](https://tube.switch.ch/videos/sBurwXgGlO) |
 |      | Wed | 29.09.2011  | 08:15 | INM202 | Labs 1               | [Labs setup](https://gitlab.epfl.ch/lara/cs320/-/blob/main/labs/labs_setup.md), [Amy Interpreter](https://gitlab.epfl.ch/lara/cs320/-/blob/main/labs/labs_01.md)         |
 |      | Thu | 30.09.2011  | 08:15 | INF119 | Labs 1     |  |
+| 3    | Mon | 04.10.2021 | 13:15 | CE1100 | Lecture 4            | [Introduction to Grammars](https://tube.switch.ch/videos/ef9ae6c1), [Syntax Trees](https://tube.switch.ch/videos/9314ac16), [LL(1) Parsing](https://tube.switch.ch/videos/38dd46b4) |