powerpoint presentation: https://docs.google.com/presentation/d/1I-ZGsfvDXLllxslVamhgaXTLGSWVFlFtjIhdD9SePMA/edit?usp=sharing
powerpoint presentation: https://docs.google.com/presentation/d/1I-ZGsfvDXLllxslVamhgaXTLGSWVFlFtjIhdD9SePMA/edit?usp=sharing