diff --git a/Source/Basics/Abstracts.cs b/Source/Basics/Abstracts.cs
index 2deb84e4..28b08ffb 100644
--- a/Source/Basics/Abstracts.cs
+++ b/Source/Basics/Abstracts.cs
@@ -145,16 +145,21 @@ public abstract class Single_TBars_Indicator : TSeries
     }
 
     // overridable Add() method to add/update a single item at the end of the list
-    public virtual void Add((System.DateTime t, double o, double h, double l, double c, double v) TBar, bool update) => base.Add((TBar.t, TBar.c), update);
+    public virtual void Add((System.DateTime t, double o, double h, double l, double c, double v) TBar, bool update) => base.Add((TBar.t, 0.0), update);
 
-    // potentially overridable Add() method for the whole series (could be replaced with faster bulk algo)
+    // potentially overridable Add() method for the whole bars or series (could be replaced with faster bulk algo)
     public virtual void Add(TBars bars)
     {
         for (int i = 0; i < bars.Count; i++) { this.Add(TBar: bars[i], update: false); }
     }
 
-    public new void Add((System.DateTime t, double v) TValue) 
-        => this.Add(TValue: TValue, update: false);
+    public virtual void Add(TSeries data)
+    {
+	    for (int i = 0; i < data.Count; i++) { base.Add(TValue: data[i], update: false); }
+    }
+
+public new void Add((System.DateTime t, double o, double h, double l, double c, double v) TBar) 
+        => this.Add(TBar: TBar, update: false);
     public void Add(bool update) 
         => this.Add(TBar: this._bars[this._bars.Count - 1], update: update);
     public void Add() 
diff --git a/Source/Indicators/ADO_Series.cs b/Source/Indicators/ADO_Series.cs
new file mode 100644
index 00000000..25db4a3f
--- /dev/null
+++ b/Source/Indicators/ADO_Series.cs
@@ -0,0 +1,45 @@
+namespace QuanTAlib;
+using System;
+
+/* <summary>
+ADO: Chaikin Accumulation/Distribution Oscillator
+    ADO measures the momentum of ADL using the difference between slow (10-day) EMA(ADL)
+    and fast (3-day) EMA(ADL):
+
+    Chaikin A/D Oscillator = (3-day EMA of ADL)  -  (10-day EMA of ADL)
+
+Sources:
+    https://school.stockcharts.com/doku.php?id=technical_indicators:chaikin_oscillator
+
+</summary> */
+
+public class ADO_Series : Single_TBars_Indicator
+{
+	private readonly ADL_Series _TSadl;
+
+	private readonly EMA_Series _TSslow;
+	private readonly EMA_Series _TSfast;
+	private readonly SUB_Series _TSado;
+
+	public ADO_Series(TBars source, bool useNaN = false) : base(source, period: 0, useNaN)
+	{
+		_TSadl = new(source: source, useNaN: false);
+		_TSslow = new(source: _TSadl, period: 10, useNaN: false);
+		_TSfast = new(source: _TSadl, period: 3, useNaN: false);
+		_TSado = new(_TSfast, _TSslow);
+
+		if (source.Count > 0)
+		{ base.Add(_TSado); }
+		Console.WriteLine(base.Count);
+	}
+
+	public override void Add((DateTime t, double o, double h, double l, double c, double v) TBar, bool update)
+	{
+		if (update)
+		{ _TSadl.Add(TBar, true); }
+
+		double _ado = this._TSado[(this.Count < this._TSado.Count) ? this.Count : this._TSado.Count - 1].v;
+		var result = (TBar.t, _ado);
+		base.Add(result, update);
+	}
+}
\ No newline at end of file
diff --git a/Tests/Validations/TA_LIB.cs b/Tests/Validations/TA_LIB.cs
index d6aaf804..95372176 100644
--- a/Tests/Validations/TA_LIB.cs
+++ b/Tests/Validations/TA_LIB.cs
@@ -109,6 +109,14 @@ public class TA_LIB
 		Assert.Equal(Math.Round(this.TALIB[this.TALIB.Length - outBegIdx - 1], 8), Math.Round(QL.Last().v, 8));
 	}
 
+	[Fact]
+	public void ADO()
+	{
+		ADO_Series QL = new(this.bars, false);
+		Core.AdOsc(this.inhigh, this.inlow, this.inclose, this.involume, 0, this.bars.Count - 1, this.TALIB, out int outBegIdx, out _);
+
+		Assert.Equal(Math.Round(this.TALIB[this.TALIB.Length - outBegIdx - 1], 8), Math.Round(QL.Last().v, 8));
+	}
 
 	[Fact]
 	public void ATR()