diff --git a/CoreIntegrationTests/CoreIntegrationTests.csproj b/CoreIntegrationTests/CoreIntegrationTests.csproj
index a3ba78f..720179b 100644
--- a/CoreIntegrationTests/CoreIntegrationTests.csproj
+++ b/CoreIntegrationTests/CoreIntegrationTests.csproj
@@ -9,13 +9,16 @@
     <PackageReference Include="Microsoft.Extensions.Identity.Stores" Version="2.1.2" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.8.0" />
     <PackageReference Include="MongoDB.Driver" Version="2.7.0" />
-    <PackageReference Include="MongoDbGenericRepository" Version="1.3.8" />
     <PackageReference Include="xunit" Version="2.4.0" />
     <PackageReference Include="xunit.runner.console" Version="2.4.0" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.0" />
     <DotNetCliToolReference Include="dotnet-xunit" Version="2.3.0-beta4-build3742" />
   </ItemGroup>
 
+  <ItemGroup>
+    <ProjectReference Include="..\MongoDbGenericRepository\MongoDbGenericRepository.csproj" />
+  </ItemGroup>
+
   <ItemGroup>
     <Reference Include="System.Configuration">
       <HintPath>..\..\..\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.6.1\System.Configuration.dll</HintPath>
diff --git a/CoreIntegrationTests/Infrastructure/MongoDbDocumentTestBase.cs b/CoreIntegrationTests/Infrastructure/MongoDbDocumentTestBase.cs
index 8c6fc2e..c70056c 100644
--- a/CoreIntegrationTests/Infrastructure/MongoDbDocumentTestBase.cs
+++ b/CoreIntegrationTests/Infrastructure/MongoDbDocumentTestBase.cs
@@ -1075,6 +1075,33 @@ namespace CoreIntegrationTests.Infrastructure
 
         #endregion Index Management
 
+        #region Math
+
+        [Fact]
+        public async Task SumByAsync()
+        {
+            // Arrange
+            var criteria = $"{GetTestName()}.{DocumentTypeName}.{Guid.NewGuid()}";
+            var documents = CreateTestDocuments(5);
+            var i = 1;
+            documents.ForEach(e =>
+            {
+                e.Nested.SomeDate = e.Nested.SomeDate.AddDays(i++);
+                e.Nested.SomeAmount = 5m;
+                e.SomeContent = criteria;
+            });
+            SUT.AddMany<T>(documents);
+            var expectedSum = documents.Sum(e => e.Nested.SomeAmount);
+
+            // Act
+            var result = await SUT.SumByAsync<T>(e => e.SomeContent == criteria, e => e.Nested.SomeAmount, PartitionKey);
+
+            // Assert
+            Assert.Equal(expectedSum, result);
+        }
+
+        #endregion Math
+
         #region Test Utils
 
         [MethodImpl(MethodImplOptions.NoInlining)]
diff --git a/CoreIntegrationTests/Infrastructure/MongoDbTKeyDocumentTestBase.cs b/CoreIntegrationTests/Infrastructure/MongoDbTKeyDocumentTestBase.cs
index 98376f5..9d99665 100644
--- a/CoreIntegrationTests/Infrastructure/MongoDbTKeyDocumentTestBase.cs
+++ b/CoreIntegrationTests/Infrastructure/MongoDbTKeyDocumentTestBase.cs
@@ -1068,6 +1068,33 @@ namespace CoreIntegrationTests.Infrastructure
 
         #endregion Index Management
 
+        #region Math
+
+        [Fact]
+        public async Task SumByAsync()
+        {
+            // Arrange
+            var criteria = $"{GetTestName()}.{DocumentTypeName}.{Guid.NewGuid()}";
+            var documents = CreateTestDocuments(5);
+            var i = 1;
+            documents.ForEach(e =>
+            {
+                e.Nested.SomeDate = e.Nested.SomeDate.AddDays(i++);
+                e.Nested.SomeAmount = 5m;
+                e.SomeContent = criteria;
+            });
+            SUT.AddMany<T, TKey>(documents);
+            var expectedSum = documents.Sum(e => e.Nested.SomeAmount);
+
+            // Act
+            var result = await SUT.SumByAsync<T, TKey>(e => e.SomeContent == criteria, e => e.Nested.SomeAmount, PartitionKey);
+
+            // Assert
+            Assert.Equal(expectedSum, result);
+        }
+
+        #endregion Math
+
         #region Test Utils
         [MethodImpl(MethodImplOptions.NoInlining)]
         private string GetCurrentMethod()
diff --git a/CoreIntegrationTests/Infrastructure/TestClasses.cs b/CoreIntegrationTests/Infrastructure/TestClasses.cs
index 20b7fc2..c9ad2b9 100644
--- a/CoreIntegrationTests/Infrastructure/TestClasses.cs
+++ b/CoreIntegrationTests/Infrastructure/TestClasses.cs
@@ -1,4 +1,5 @@
-using MongoDB.Bson.Serialization.Attributes;
+using MongoDB.Bson;
+using MongoDB.Bson.Serialization.Attributes;
 using MongoDbGenericRepository.Models;
 using MongoDbGenericRepository.Utils;
 using System;
@@ -21,6 +22,8 @@ namespace CoreIntegrationTests.Infrastructure
     public class Nested
     {
         public DateTime SomeDate { get; set; }
+        [BsonRepresentation(BsonType.Decimal128)]
+        public decimal SomeAmount { get; set; }
     }
 
     public class Child
diff --git a/MongoDbGenericRepository/Abstractions/IReadOnlyMongoRepository.cs b/MongoDbGenericRepository/Abstractions/IReadOnlyMongoRepository.cs
index 2632d66..a79d3e9 100644
--- a/MongoDbGenericRepository/Abstractions/IReadOnlyMongoRepository.cs
+++ b/MongoDbGenericRepository/Abstractions/IReadOnlyMongoRepository.cs
@@ -425,6 +425,34 @@ namespace MongoDbGenericRepository
             where TKey : IEquatable<TKey>;
 
         #endregion
+
+        #region Sum
+
+        /// <summary>
+        /// Sums the values of a selected field for a given filtered collection of documents.
+        /// </summary>
+        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
+        /// <param name="filter">A LINQ expression filter.</param>
+        /// <param name="selector">The field you want to sum.</param>
+        /// <param name="partitionKey">The partition key of your document, if any.</param>
+        Task<decimal> SumByAsync<TDocument>(Expression<Func<TDocument, bool>> filter, 
+            Expression<Func<TDocument, decimal>> selector,
+            string partitionKey = null)
+            where TDocument : IDocument;
+
+        /// <summary>
+        /// Sums the values of a selected field for a given filtered collection of documents.
+        /// </summary>
+        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
+        /// <param name="filter">A LINQ expression filter.</param>
+        /// <param name="selector">The field you want to sum.</param>
+        /// <param name="partitionKey">The partition key of your document, if any.</param>
+        Task<decimal> SumByAsync<TDocument, TKey>(Expression<Func<TDocument, bool>> filter,
+                                                       Expression<Func<TDocument, decimal>> selector,
+                                                       string partitionKey = null)
+            where TDocument : IDocument<TKey>
+            where TKey : IEquatable<TKey>;
+        #endregion Sum
     }
 
 }
diff --git a/MongoDbGenericRepository/BaseMongoDbRepository.cs b/MongoDbGenericRepository/BaseMongoDbRepository.cs
index 2a3f07e..f8c9c75 100644
--- a/MongoDbGenericRepository/BaseMongoDbRepository.cs
+++ b/MongoDbGenericRepository/BaseMongoDbRepository.cs
@@ -1022,10 +1022,46 @@ namespace MongoDbGenericRepository
         /// </summary>
         /// <typeparam name="TDocument">The type representing a Document.</typeparam>
         /// <param name="filter">A LINQ expression filter.</param>
+        /// <param name="sortSelector">The property selector.</param>
+        /// <param name="ascending">Order of the sorting.</param>
         /// <param name="skipNumber">The number of documents you want to skip. Default value is 0.</param>
         /// <param name="takeNumber">The number of documents you want to take. Default value is 50.</param>
         /// <param name="partitionKey">An optional partition key.</param>
-        public virtual async Task<List<TDocument>> GetPaginatedAsync<TDocument>(Expression<Func<TDocument, bool>> filter, int skipNumber = 0, int takeNumber = 50, string partitionKey = null)
+        public virtual async Task<List<TDocument>> GetSortedPaginatedAsync<TDocument>(
+            Expression<Func<TDocument, bool>> filter,
+            Expression<Func<TDocument, object>> sortSelector,
+            bool ascending = true,
+            int skipNumber = 0,
+            int takeNumber = 50,
+            string partitionKey = null)
+            where TDocument : IDocument
+        {
+            var sorting = ascending
+                ? Builders<TDocument>.Sort.Ascending(sortSelector)
+                : Builders<TDocument>.Sort.Descending(sortSelector);
+
+            return await HandlePartitioned<TDocument>(partitionKey)
+                    .Find(filter)
+                    .Sort(sorting)
+                    .Skip(skipNumber)
+                    .Limit(takeNumber)
+                    .ToListAsync();
+        }
+
+
+        /// <summary>
+        /// Asynchronously returns a paginated list of the documents matching the filter condition.
+        /// </summary>
+        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
+        /// <param name="filter">A LINQ expression filter.</param>
+        /// <param name="skipNumber">The number of documents you want to skip. Default value is 0.</param>
+        /// <param name="takeNumber">The number of documents you want to take. Default value is 50.</param>
+        /// <param name="partitionKey">An optional partition key.</param>
+        public virtual async Task<List<TDocument>> GetPaginatedAsync<TDocument>(
+            Expression<Func<TDocument, bool>> filter, 
+            int skipNumber = 0, 
+            int takeNumber = 50, 
+            string partitionKey = null)
             where TDocument : IDocument
         {
             return await HandlePartitioned<TDocument>(partitionKey).Find(filter).Skip(skipNumber).Limit(takeNumber).ToListAsync();
diff --git a/MongoDbGenericRepository/BaseMongoDbRepository.Maths.cs b/MongoDbGenericRepository/ReadOnlyMongoRepository.Maths.cs
similarity index 50%
rename from MongoDbGenericRepository/BaseMongoDbRepository.Maths.cs
rename to MongoDbGenericRepository/ReadOnlyMongoRepository.Maths.cs
index bbc6552..b75fe11 100644
--- a/MongoDbGenericRepository/BaseMongoDbRepository.Maths.cs
+++ b/MongoDbGenericRepository/ReadOnlyMongoRepository.Maths.cs
@@ -12,7 +12,7 @@ namespace MongoDbGenericRepository
     /// The base Repository, it is meant to be inherited from by your custom custom MongoRepository implementation.
     /// Its constructor must be given a connection string and a database name.
     /// </summary>
-    public abstract partial class BaseMongoRepository : ReadOnlyMongoRepository, IBaseMongoRepository
+    public abstract partial class ReadOnlyMongoRepository
     {
         /// <summary>
         /// Sums the values of a selected field for a given filtered collection of documents.
@@ -26,11 +26,26 @@ namespace MongoDbGenericRepository
                                                        string partitionKey = null)
                                                        where TDocument : IDocument
         {
-            var collection = string.IsNullOrEmpty(partitionKey) ? GetCollection<TDocument>() : GetCollection<TDocument>(partitionKey);
+            return await SumByAsync<TDocument, Guid>(filter, selector, partitionKey);
+        }
 
-            return await collection.AsQueryable()
-                                   .Where(filter)
-                                   .SumAsync(selector);
+        /// <summary>
+        /// Sums the values of a selected field for a given filtered collection of documents.
+        /// </summary>
+        /// <typeparam name="TDocument">The type representing a Document.</typeparam>
+        /// <param name="filter">A LINQ expression filter.</param>
+        /// <param name="selector">The field you want to sum.</param>
+        /// <param name="partitionKey">The partition key of your document, if any.</param>
+        public virtual async Task<decimal> SumByAsync<TDocument, TKey>(Expression<Func<TDocument, bool>> filter,
+                                                       Expression<Func<TDocument, decimal>> selector,
+                                                       string partitionKey = null)
+            where TDocument : IDocument<TKey>
+            where TKey : IEquatable<TKey>
+        {
+            return await GetCollection<TDocument, TKey>(partitionKey)
+                                                .AsQueryable()
+                                                .Where(filter)
+                                                .SumAsync(selector);
         }
 
     }
diff --git a/MongoDbGenericRepository/ReadOnlyMongoRepository.cs b/MongoDbGenericRepository/ReadOnlyMongoRepository.cs
index 0a8adb9..7638cdb 100644
--- a/MongoDbGenericRepository/ReadOnlyMongoRepository.cs
+++ b/MongoDbGenericRepository/ReadOnlyMongoRepository.cs
@@ -11,7 +11,7 @@ namespace MongoDbGenericRepository
     /// <summary>
     /// The ReadOnlyMongoRepository implements the readonly functionality of the IReadOnlyMongoRepository.
     /// </summary>
-    public class ReadOnlyMongoRepository : IReadOnlyMongoRepository
+    public abstract partial class ReadOnlyMongoRepository : IReadOnlyMongoRepository
     {
         /// <summary>
         /// The connection string.
@@ -578,7 +578,7 @@ namespace MongoDbGenericRepository
         /// <param name="filter">A LINQ expression filter.</param>
         /// <param name="minValueSelector">A property selector to order by ascending.</param>
         /// <param name="partitionKey">An optional partition key.</param>
-        public async Task<TValue> GetMinValueAsync<TDocument, TValue>(Expression<Func<TDocument, bool>> filter, Expression<Func<TDocument, TValue>> minValueSelector, string partitionKey = null)
+        public virtual async Task<TValue> GetMinValueAsync<TDocument, TValue>(Expression<Func<TDocument, bool>> filter, Expression<Func<TDocument, TValue>> minValueSelector, string partitionKey = null)
             where TDocument : IDocument
         {
             return await GetMinValueAsync<TDocument, Guid, TValue>(filter, minValueSelector, partitionKey);
@@ -593,7 +593,7 @@ namespace MongoDbGenericRepository
         /// <param name="filter">A LINQ expression filter.</param>
         /// <param name="minValueSelector">A property selector to order by ascending.</param>
         /// <param name="partitionKey">An optional partition key.</param>
-        public async Task<TValue> GetMinValueAsync<TDocument, TKey, TValue>(Expression<Func<TDocument, bool>> filter, Expression<Func<TDocument, TValue>> minValueSelector, string partitionKey = null)
+        public virtual async Task<TValue> GetMinValueAsync<TDocument, TKey, TValue>(Expression<Func<TDocument, bool>> filter, Expression<Func<TDocument, TValue>> minValueSelector, string partitionKey = null)
             where TDocument : IDocument<TKey>
             where TKey : IEquatable<TKey>
         {
@@ -608,7 +608,7 @@ namespace MongoDbGenericRepository
         /// <param name="filter">A LINQ expression filter.</param>
         /// <param name="minValueSelector">A property selector to order by ascending.</param>
         /// <param name="partitionKey">An optional partition key.</param>
-        public TValue GetMinValue<TDocument, TValue>(Expression<Func<TDocument, bool>> filter, Expression<Func<TDocument, TValue>> minValueSelector, string partitionKey = null)
+        public virtual TValue GetMinValue<TDocument, TValue>(Expression<Func<TDocument, bool>> filter, Expression<Func<TDocument, TValue>> minValueSelector, string partitionKey = null)
             where TDocument : IDocument
         {
             return GetMinValue<TDocument, Guid, TValue>(filter, minValueSelector, partitionKey);
@@ -623,7 +623,7 @@ namespace MongoDbGenericRepository
         /// <param name="filter">A LINQ expression filter.</param>
         /// <param name="minValueSelector">A property selector to order by ascending.</param>
         /// <param name="partitionKey">An optional partition key.</param>
-        public TValue GetMinValue<TDocument, TKey, TValue>(Expression<Func<TDocument, bool>> filter, Expression<Func<TDocument, TValue>> minValueSelector, string partitionKey = null)
+        public virtual TValue GetMinValue<TDocument, TKey, TValue>(Expression<Func<TDocument, bool>> filter, Expression<Func<TDocument, TValue>> minValueSelector, string partitionKey = null)
             where TDocument : IDocument<TKey>
             where TKey : IEquatable<TKey>
         {
@@ -640,7 +640,7 @@ namespace MongoDbGenericRepository
         /// <typeparam name="TDocument">The document type.</typeparam>
         /// <param name="partitionKey">An optional partition key.</param>
         /// <returns>An <see cref="IMongoCollection{TDocument}"/></returns>
-        protected IMongoCollection<TDocument> GetCollection<TDocument>(string partitionKey = null) where TDocument : IDocument
+        protected virtual IMongoCollection<TDocument> GetCollection<TDocument>(string partitionKey = null) where TDocument : IDocument
         {
             return MongoDbContext.GetCollection<TDocument>(partitionKey);
         }
@@ -651,7 +651,7 @@ namespace MongoDbGenericRepository
         /// <typeparam name="TDocument">The document type.</typeparam>
         /// <param name="document">The document.</param>
         /// <returns></returns>
-        protected IMongoCollection<TDocument> HandlePartitioned<TDocument>(TDocument document) where TDocument : IDocument
+        protected virtual IMongoCollection<TDocument> HandlePartitioned<TDocument>(TDocument document) where TDocument : IDocument
         {
             if (document is IPartitionedDocument)
             {
@@ -667,7 +667,7 @@ namespace MongoDbGenericRepository
         /// <typeparam name="TKey">The type of the primary key.</typeparam>
         /// <param name="document">The document.</param>
         /// <returns></returns>
-        protected IMongoCollection<TDocument> HandlePartitioned<TDocument, TKey>(TDocument document)
+        protected virtual IMongoCollection<TDocument> HandlePartitioned<TDocument, TKey>(TDocument document)
             where TDocument : IDocument<TKey>
             where TKey : IEquatable<TKey>
         {
@@ -684,7 +684,7 @@ namespace MongoDbGenericRepository
         /// <typeparam name="TDocument">The document type.</typeparam>
         /// <param name="partitionKey">The collection partition key.</param>
         /// <returns></returns>
-        protected IMongoCollection<TDocument> HandlePartitioned<TDocument>(string partitionKey) where TDocument : IDocument
+        protected virtual IMongoCollection<TDocument> HandlePartitioned<TDocument>(string partitionKey) where TDocument : IDocument
         {
             if (!string.IsNullOrEmpty(partitionKey))
             {
@@ -700,7 +700,7 @@ namespace MongoDbGenericRepository
         /// <typeparam name="TKey">The type of the primary key.</typeparam>
         /// <param name="partitionKey">The collection partition key.</param>
         /// <returns></returns>
-        protected IMongoCollection<TDocument> GetCollection<TDocument, TKey>(string partitionKey = null)
+        protected virtual IMongoCollection<TDocument> GetCollection<TDocument, TKey>(string partitionKey = null)
             where TDocument : IDocument<TKey>
             where TKey : IEquatable<TKey>
         {
@@ -714,7 +714,7 @@ namespace MongoDbGenericRepository
         /// <typeparam name="TKey">The type of the primary key.</typeparam>
         /// <param name="partitionKey">The collection partition key.</param>
         /// <returns></returns>
-        protected IMongoCollection<TDocument> HandlePartitioned<TDocument, TKey>(string partitionKey)
+        protected virtual IMongoCollection<TDocument> HandlePartitioned<TDocument, TKey>(string partitionKey)
             where TDocument : IDocument<TKey>
             where TKey : IEquatable<TKey>
         {