Automating Trading Strategies in MQL5 (Part 25): Trendline Trader with Least Squares Fit and Dynamic Signal Generation - https://www.mql5.com/en/articles/19077
MQL5 Wizard Techniques you should know (Part 78): Using Gator Oscillator and the Accumulation/Distribution Oscillator - https://www.mql5.com/en/articles/18992