diff --git a/src/R3/Operators/_Operators.cs b/src/R3/Operators/_Operators.cs
index 853b286f..9306cc9c 100644
--- a/src/R3/Operators/_Operators.cs
+++ b/src/R3/Operators/_Operators.cs
@@ -37,29 +37,56 @@ public static ConnectableObservable<T> Multicast<T>(this Observable<T> source, I
         return new Multicast<T>(source, subject);
     }
 
-    public static Observable<T> Publish<T>(this Observable<T> source)
+    public static ConnectableObservable<T> Publish<T>(this Observable<T> source)
     {
         return source.Multicast(new Subject<T>());
     }
 
-    public static Observable<T> Publish<T>(this Observable<T> source, T initialValue)
+    public static ConnectableObservable<T> Publish<T>(this Observable<T> source, T initialValue)
     {
-        return source.Multicast(new ReactiveProperty<T>(initialValue));
+        return source.Multicast(new ReactiveProperty<T>(initialValue, equalityComparer: null));
     }
 
-    // TODO: ReplaySubject
-    //public static Observable<T> Replay<T>(this Observable<T> source)
-    //{
-    //    return source.Multicast(new ReplaySubject<T>());
-    //}
+    public static ConnectableObservable<T> Replay<T>(this Observable<T> source)
+    {
+        return source.Multicast(new ReplaySubject<T>());
+    }
 
-    // TODO: require RefCount
-    //public static Observable<T> Share<T>(this Observable<T> source)
-    //{
-    //    return source.Publish().RefCount();
-    //}
-}
+    public static ConnectableObservable<T> Replay<T>(this Observable<T> source, int bufferSize)
+    {
+        return source.Multicast(new ReplaySubject<T>(bufferSize));
+    }
+
+    public static ConnectableObservable<T> Replay<T>(this Observable<T> source, TimeSpan window)
+    {
+        return source.Multicast(new ReplaySubject<T>(window));
+    }
+
+    public static ConnectableObservable<T> Replay<T>(this Observable<T> source, TimeSpan window, TimeProvider timeProvider)
+    {
+        return source.Multicast(new ReplaySubject<T>(window, timeProvider));
+    }
+
+    public static ConnectableObservable<T> Replay<T>(this Observable<T> source, int bufferSize, TimeSpan window)
+    {
+        return source.Multicast(new ReplaySubject<T>(bufferSize, window));
+    }
 
+    public static ConnectableObservable<T> Replay<T>(this Observable<T> source, int bufferSize, TimeSpan window, TimeProvider timeProvider)
+    {
+        return source.Multicast(new ReplaySubject<T>(bufferSize, window, timeProvider));
+    }
+
+    public static Observable<T> RefCount<T>(this ConnectableObservable<T> source)
+    {
+        return new RefCount<T>(source);
+    }
+
+    public static Observable<T> Share<T>(this Observable<T> source)
+    {
+        return source.Publish().RefCount();
+    }
+}
 
 public abstract class ConnectableObservable<T> : Observable<T>
 {
@@ -106,3 +133,53 @@ public void Dispose()
         }
     }
 }
+
+internal sealed class RefCount<T>(ConnectableObservable<T> source) : Observable<T>
+{
+    readonly object gate = new object();
+    int refCount = 0;
+    IDisposable? connection;
+
+    protected override IDisposable SubscribeCore(Observer<T> observer)
+    {
+        lock (gate)
+        {
+            var subcription = source.Subscribe(new _RefCount(this, observer));
+            if (++refCount == 1)
+            {
+                connection = source.Connect();
+            }
+            return subcription;
+        }
+    }
+
+    sealed class _RefCount(RefCount<T> parent, Observer<T> observer) : Observer<T>
+    {
+        protected override void OnNextCore(T value)
+        {
+            observer.OnNext(value);
+        }
+
+        protected override void OnErrorResumeCore(Exception error)
+        {
+            observer.OnErrorResume(error);
+        }
+
+        protected override void OnCompletedCore(Result result)
+        {
+            observer.OnCompleted(result);
+        }
+
+        protected override void DisposeCore()
+        {
+            lock (parent.gate)
+            {
+                if (--parent.refCount == 0)
+                {
+                    parent.connection?.Dispose();
+                    parent.connection = null;
+                }
+            }
+        }
+    }
+}
diff --git a/src/R3/ReplaySubject.cs b/src/R3/ReplaySubject.cs
index 065ed650..9efb885f 100644
--- a/src/R3/ReplaySubject.cs
+++ b/src/R3/ReplaySubject.cs
@@ -31,6 +31,11 @@ public ReplaySubject(TimeSpan window, TimeProvider timeProvider)
     {
     }
 
+    public ReplaySubject(int bufferSize, TimeSpan window)
+        : this(bufferSize, window, ObservableSystem.DefaultTimeProvider)
+    {
+    }
+
     // full constructor
     public ReplaySubject(int bufferSize, TimeSpan window, TimeProvider timeProvider)
     {