1.Definition of 𝜎−𝑓𝑖𝑒𝑙𝑑, 𝜋−𝑠𝑦𝑠𝑡𝑒𝑚 𝑎𝑛𝑑 𝜆−𝑠𝑦𝑠𝑡𝑒𝑚.

2.Introduction to Dynkin's Theorem.

3.Some lemmas for proof of Dynkin’s Theorem

4.Proof of Dynkin’s Theorem.