https://www.alphavantage.co/documentation/#dailyadj
example: https://www.alphavantage.co/query?function=TIME_SERIES_DAILY_ADJUSTED&symbol=MSFT&datatype=csv&apikey=demo
timestamp,open,high,low,close,adjusted_close,volume,dividend_amount,split_coefficient
2018-05-22,97.6800,98.1700,97.2000,97.5950,97.5950,9711773,0.0000,1.0000
2018-05-21,97.0000,98.0100,96.8000,97.6000,97.6000,18996380,0.0000,1.0000