diff --git a/src/core-taggeds-optional/Optional.Tests.Old/OptionalLinqExtensions.Tests/ElementAtOrAbsent.Enumerable.Int64.cs b/src/core-taggeds-optional/Optional.Tests.Old/OptionalLinqExtensions.Tests/ElementAtOrAbsent.Enumerable.Int64.cs
deleted file mode 100644
index d424d8ef..00000000
--- a/src/core-taggeds-optional/Optional.Tests.Old/OptionalLinqExtensions.Tests/ElementAtOrAbsent.Enumerable.Int64.cs
+++ /dev/null
@@ -1,69 +0,0 @@
-using PrimeFuncPack.UnitTest;
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using static PrimeFuncPack.UnitTest.TestData;
-
-namespace PrimeFuncPack.Core.Tests;
-
-partial class OptionalLinqExtensionsTests
-{
-    [Test]
-    public void ElementAtOrAbsentByLong_CollectionSourceIsNull_ExpectArgumentNullException()
-    {
-        IEnumerable<StructType> source = null!;
-        long index = 1;
-
-        var ex = Assert.Throws<ArgumentNullException>(() => _ = source.ElementAtOrAbsent(index));
-        Assert.That(ex!.ParamName, Is.EqualTo("source"));
-    }
-
-    [Test]
-    [TestCase(0)]
-    [TestCase(1)]
-    [TestCase(2)]
-    public void ElementAtOrAbsentByLong_CollectionIndexIsInRange_ExpectPresentItem(
-        long index)
-    {
-        var source = CreateCollection<StructType?>(SomeTextStructType, NullTextStructType, null);
-        var actual = source.ElementAtOrAbsent(index);
-
-        var expectedValue = source.ElementAt(checked((int)index));
-        var expected = Optional<StructType?>.Present(expectedValue);
-
-        Assert.That(actual, Is.EqualTo(expected));
-    }
-
-    [Test]
-    [TestCase(long.MinValue)]
-    [TestCase(-1)]
-    [TestCase(3)]
-    [TestCase(long.MaxValue)]
-    public void ElementAtOrAbsentByLong_CollectionIndexIsNotInRange_ExpectAbsent(
-        long index)
-    {
-        var source = CreateCollection(PlusFifteenIdRefType, MinusFifteenIdRefType, ZeroIdRefType);
-
-        var actual = source.ElementAtOrAbsent(index);
-        var expected = Optional<RefType>.Absent;
-
-        Assert.That(actual, Is.EqualTo(expected));
-    }
-
-    [Test]
-    [TestCase(long.MinValue)]
-    [TestCase(-1)]
-    [TestCase(0)]
-    [TestCase(1)]
-    [TestCase(long.MaxValue)]
-    public void ElementAtOrAbsentByLong_CollectionIsEmpty_ExpectAbsent(
-        long index)
-    {
-        var source = CreateCollection<RefType>();
-
-        var actual = source.ElementAtOrAbsent(index);
-        var expected = Optional<RefType>.Absent;
-
-        Assert.That(actual, Is.EqualTo(expected));
-    }
-}
diff --git a/src/core-taggeds-optional/Optional.Tests.Old/OptionalLinqExtensions.Tests/ElementAtOrAbsent.List.Int64.cs b/src/core-taggeds-optional/Optional.Tests.Old/OptionalLinqExtensions.Tests/ElementAtOrAbsent.List.Int64.cs
deleted file mode 100644
index 462ece29..00000000
--- a/src/core-taggeds-optional/Optional.Tests.Old/OptionalLinqExtensions.Tests/ElementAtOrAbsent.List.Int64.cs
+++ /dev/null
@@ -1,73 +0,0 @@
-using PrimeFuncPack.UnitTest;
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using static PrimeFuncPack.UnitTest.TestData;
-
-namespace PrimeFuncPack.Core.Tests;
-
-partial class OptionalLinqExtensionsTests
-{
-    [Test]
-    public void ElementAtOrAbsentByLong_ListSourceIsNull_ExpectArgumentNullException()
-    {
-        IList<StructType> source = null!;
-        long index = 1;
-
-        var ex = Assert.Throws<ArgumentNullException>(Test);
-        Assert.That(ex!.ParamName, Is.EqualTo("source"));
-
-        void Test()
-            =>
-            _ = source.ElementAtOrAbsent(index);
-    }
-
-    [Test]
-    [TestCase(0)]
-    [TestCase(1)]
-    [TestCase(2)]
-    public void ElementAtOrAbsentByLong_ListIndexIsInRange_ExpectPresentItem(
-        long index)
-    {
-        var source = CreateList(NullTextStructType, SomeTextStructType, SomeTextStructType);
-        var actual = source.ElementAtOrAbsent(index);
-
-        var expectedValue = source.ElementAt(checked((int)index));
-        var expected = Optional<StructType>.Present(expectedValue);
-
-        Assert.That(actual, Is.EqualTo(expected));
-    }
-
-    [Test]
-    [TestCase(long.MinValue)]
-    [TestCase(-1)]
-    [TestCase(4)]
-    [TestCase(long.MaxValue)]
-    public void ElementAtOrAbsentByLong_ListIndexIsNotInRange_ExpectAbsent(
-        long index)
-    {
-        var source = CreateList(PlusFifteenIdRefType, MinusFifteenIdRefType, ZeroIdRefType, null);
-
-        var actual = source.ElementAtOrAbsent(index);
-        var expected = Optional<RefType?>.Absent;
-
-        Assert.That(actual, Is.EqualTo(expected));
-    }
-
-    [Test]
-    [TestCase(long.MinValue)]
-    [TestCase(-1)]
-    [TestCase(0)]
-    [TestCase(1)]
-    [TestCase(long.MaxValue)]
-    public void ElementAtOrAbsentByLong_ListIsEmpty_ExpectAbsent(
-        long index)
-    {
-        var source = CreateList<RefType>();
-
-        var actual = source.ElementAtOrAbsent(index);
-        var expected = Optional<RefType>.Absent;
-
-        Assert.That(actual, Is.EqualTo(expected));
-    }
-}
diff --git a/src/core-taggeds-optional/Optional.Tests.Old/OptionalLinqExtensions.Tests/ElementAtOrAbsent.ReadOnlyList.Int64.cs b/src/core-taggeds-optional/Optional.Tests.Old/OptionalLinqExtensions.Tests/ElementAtOrAbsent.ReadOnlyList.Int64.cs
deleted file mode 100644
index 06302d78..00000000
--- a/src/core-taggeds-optional/Optional.Tests.Old/OptionalLinqExtensions.Tests/ElementAtOrAbsent.ReadOnlyList.Int64.cs
+++ /dev/null
@@ -1,73 +0,0 @@
-using PrimeFuncPack.UnitTest;
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using static PrimeFuncPack.UnitTest.TestData;
-
-namespace PrimeFuncPack.Core.Tests;
-
-partial class OptionalLinqExtensionsTests
-{
-    [Test]
-    public void ElementAtOrAbsentByLong_ReadOnlyListSourceIsNull_ExpectArgumentNullException()
-    {
-        IReadOnlyList<StructType> source = null!;
-        long index = 1;
-
-        var ex = Assert.Throws<ArgumentNullException>(Test);
-        Assert.That(ex!.ParamName, Is.EqualTo("source"));
-
-        void Test()
-            =>
-            _ = source.ElementAtOrAbsent(index);
-    }
-
-    [Test]
-    [TestCase(0)]
-    [TestCase(1)]
-    [TestCase(2)]
-    public void ElementAtOrAbsentByLong_ReadOnlyListIndexIsInRange_ExpectPresentItem(
-        long index)
-    {
-        var source = CreateReadOnlyList(PlusFifteenIdRefType, null, ZeroIdRefType);
-        var actual = source.ElementAtOrAbsent(index);
-
-        var expectedValue = source.ElementAt(checked((int)index));
-        var expected = Optional<RefType?>.Present(expectedValue);
-
-        Assert.That(actual, Is.EqualTo(expected));
-    }
-
-    [Test]
-    [TestCase(long.MinValue)]
-    [TestCase(-1)]
-    [TestCase(4)]
-    [TestCase(long.MaxValue)]
-    public void ElementAtOrAbsentByLong_ReadOnlyListIndexIsNotInRange_ExpectAbsent(
-        long index)
-    {
-        var source = CreateReadOnlyList(PlusFifteenIdRefType, MinusFifteenIdRefType, ZeroIdRefType, null);
-
-        var actual = source.ElementAtOrAbsent(index);
-        var expected = Optional<RefType?>.Absent;
-
-        Assert.That(actual, Is.EqualTo(expected));
-    }
-
-    [Test]
-    [TestCase(long.MinValue)]
-    [TestCase(-1)]
-    [TestCase(0)]
-    [TestCase(1)]
-    [TestCase(long.MaxValue)]
-    public void ElementAtOrAbsentByLong_ReadOnlyListIsEmpty_ExpectAbsent(
-        long index)
-    {
-        var source = CreateReadOnlyList<RefType>();
-
-        var actual = source.ElementAtOrAbsent(index);
-        var expected = Optional<RefType>.Absent;
-
-        Assert.That(actual, Is.EqualTo(expected));
-    }
-}
diff --git a/src/core-taggeds-optional/Optional/OptionalLinqExtensions/ElementAtOrAbsent.cs b/src/core-taggeds-optional/Optional/OptionalLinqExtensions/ElementAtOrAbsent.cs
index fef00fc0..73566a88 100644
--- a/src/core-taggeds-optional/Optional/OptionalLinqExtensions/ElementAtOrAbsent.cs
+++ b/src/core-taggeds-optional/Optional/OptionalLinqExtensions/ElementAtOrAbsent.cs
@@ -19,12 +19,4 @@ public static Optional<TSource> ElementAtOrAbsent<TSource>(
         InnerElementAtOrAbsent(
             source ?? throw new ArgumentNullException(nameof(source)),
             index);
-
-    public static Optional<TSource> ElementAtOrAbsent<TSource>(
-        this IEnumerable<TSource> source,
-        long index)
-        =>
-        InnerElementAtOrAbsent(
-            source ?? throw new ArgumentNullException(nameof(source)),
-            index);
 }
diff --git a/src/core-taggeds-optional/Optional/OptionalLinqExtensions/Inner/InnerElementAtOrAbsent.cs b/src/core-taggeds-optional/Optional/OptionalLinqExtensions/Inner/InnerElementAtOrAbsent.cs
index dfc3ce16..00388d9a 100644
--- a/src/core-taggeds-optional/Optional/OptionalLinqExtensions/Inner/InnerElementAtOrAbsent.cs
+++ b/src/core-taggeds-optional/Optional/OptionalLinqExtensions/Inner/InnerElementAtOrAbsent.cs
@@ -37,24 +37,6 @@ IList<TSource> list
             =>
             list.InnerElementAtOrAbsent_IList(index),
 
-            _ =>
-            source.InnerElementAtOrAbsent_IEnumerable(index)
-        };
-
-    private static Optional<TSource> InnerElementAtOrAbsent<TSource>(
-        this IEnumerable<TSource> source,
-        long index)
-        =>
-        source switch
-        {
-            IReadOnlyList<TSource> list
-            =>
-            list.InnerElementAtOrAbsent_IReadOnlyList(index),
-
-            IList<TSource> list
-            =>
-            list.InnerElementAtOrAbsent_IList(index),
-
             _ =>
             source.InnerElementAtOrAbsent_IEnumerable(index)
         };
diff --git a/src/core-taggeds-optional/Optional/OptionalLinqExtensions/Inner/InnerElementAtOrAbsent_IEnumerable.cs b/src/core-taggeds-optional/Optional/OptionalLinqExtensions/Inner/InnerElementAtOrAbsent_IEnumerable.cs
index 6af84211..f400f876 100644
--- a/src/core-taggeds-optional/Optional/OptionalLinqExtensions/Inner/InnerElementAtOrAbsent_IEnumerable.cs
+++ b/src/core-taggeds-optional/Optional/OptionalLinqExtensions/Inner/InnerElementAtOrAbsent_IEnumerable.cs
@@ -31,32 +31,4 @@ private static Optional<TSource> InnerElementAtOrAbsent_IEnumerable<TSource>(
 
         return default;
     }
-
-    private static Optional<TSource> InnerElementAtOrAbsent_IEnumerable<TSource>(
-        this IEnumerable<TSource> source,
-        long index)
-    {
-        if (index >= 0)
-        {
-            using var enumerator = source.GetEnumerator();
-
-            if (enumerator.MoveNext())
-            {
-                var countdownIndex = index;
-
-                do
-                {
-                    if (countdownIndex == 0)
-                    {
-                        return new(enumerator.Current);
-                    }
-
-                    countdownIndex--;
-                }
-                while (enumerator.MoveNext());
-            }
-        }
-
-        return default;
-    }
 }
diff --git a/src/core-taggeds-optional/Optional/OptionalLinqExtensions/Inner/InnerElementAtOrAbsent_IList.cs b/src/core-taggeds-optional/Optional/OptionalLinqExtensions/Inner/InnerElementAtOrAbsent_IList.cs
index 2cffea7f..e572dea1 100644
--- a/src/core-taggeds-optional/Optional/OptionalLinqExtensions/Inner/InnerElementAtOrAbsent_IList.cs
+++ b/src/core-taggeds-optional/Optional/OptionalLinqExtensions/Inner/InnerElementAtOrAbsent_IList.cs
@@ -9,10 +9,4 @@ private static Optional<TSource> InnerElementAtOrAbsent_IList<TSource>(
         int index)
         =>
         index >= 0 && index < source.Count ? new(source[index]) : default;
-
-    private static Optional<TSource> InnerElementAtOrAbsent_IList<TSource>(
-        this IList<TSource> source,
-        long index)
-        =>
-        index >= 0 && index < source.Count ? new(source[(int)index]) : default;
 }
diff --git a/src/core-taggeds-optional/Optional/OptionalLinqExtensions/Inner/InnerElementAtOrAbsent_IReadOnlyList.cs b/src/core-taggeds-optional/Optional/OptionalLinqExtensions/Inner/InnerElementAtOrAbsent_IReadOnlyList.cs
index 76c06a74..a1d8e9e4 100644
--- a/src/core-taggeds-optional/Optional/OptionalLinqExtensions/Inner/InnerElementAtOrAbsent_IReadOnlyList.cs
+++ b/src/core-taggeds-optional/Optional/OptionalLinqExtensions/Inner/InnerElementAtOrAbsent_IReadOnlyList.cs
@@ -9,10 +9,4 @@ private static Optional<TSource> InnerElementAtOrAbsent_IReadOnlyList<TSource>(
         int index)
         =>
         index >= 0 && index < source.Count ? new(source[index]) : default;
-
-    private static Optional<TSource> InnerElementAtOrAbsent_IReadOnlyList<TSource>(
-        this IReadOnlyList<TSource> source,
-        long index)
-        =>
-        index >= 0 && index < source.Count ? new(source[(int)index]) : default;
 }