diff --git a/README.md b/README.md
index 9000506..b6b816f 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@ Answers to [openfullstack.com](https://fullstackopen.com) course exercises from
   _Details solutions: [4.1](https://github.com/patchamama/fullstackopen-part4-bloglist/commit/01104c7798ad53f35ee73994826f5cc3602b9b3e) | [4.2](https://github.com/patchamama/fullstackopen-part4-bloglist/commit/7c913309759236084783f4bdfdec443c5b9e19d5)_
 
 - [Exercises 4.3.-4.7.](https://fullstackopen.com/en/part4/structure_of_backend_application_introduction_to_testing#exercises-4-3-4-7)
-  _Details solutions: [4.3](https://github.com/patchamama/fullstackopen-part4-bloglist/commit/0f1a759e78310de711531ed481917496e2f50ec8) | [4.4](https://github.com/patchamama/fullstackopen-part4-bloglist/commit/2585dc72841e8382123fa481aa149d19dd611482) | [4.5]() | [4.6]() | [4.7]()_
+  _Details solutions: [4.3](https://github.com/patchamama/fullstackopen-part4-bloglist/commit/0f1a759e78310de711531ed481917496e2f50ec8) | [4.4](https://github.com/patchamama/fullstackopen-part4-bloglist/commit/2585dc72841e8382123fa481aa149d19dd611482) | [4.5](https://github.com/patchamama/fullstackopen-part4-bloglist/commit/4fd94b8779e33ea32b3703a6e6a823291d247e0c) | [4.6]() | [4.7]()_
 
 ### b. Testing the backend
 
diff --git a/package-lock.json b/package-lock.json
index be2907a..38357dc 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -12,6 +12,7 @@
         "cors": "2.8.5",
         "dotenv": "16.3.1",
         "express": "4.18.2",
+        "lodash": "^4.17.21",
         "mongoose": "7.5.0"
       },
       "devDependencies": {
@@ -3902,6 +3903,11 @@
         "url": "https://github.com/sponsors/sindresorhus"
       }
     },
+    "node_modules/lodash": {
+      "version": "4.17.21",
+      "resolved": "https://registry.npmjs.org/lodash/-/lodash-4.17.21.tgz",
+      "integrity": "sha512-v2kDEe57lecTulaDIuNTPy3Ry4gLGJ6Z1O3vE1krgXZNrsQ+LFTGHVxVjcXPs17LhbZVGedAJv8XZ1tvj5FvSg=="
+    },
     "node_modules/lodash.merge": {
       "version": "4.6.2",
       "resolved": "https://registry.npmjs.org/lodash.merge/-/lodash.merge-4.6.2.tgz",
diff --git a/package.json b/package.json
index 7d248c1..f43e2ef 100644
--- a/package.json
+++ b/package.json
@@ -23,6 +23,7 @@
     "cors": "2.8.5",
     "dotenv": "16.3.1",
     "express": "4.18.2",
+    "lodash": "^4.17.21",
     "mongoose": "7.5.0"
   },
   "devDependencies": {
diff --git a/tests/blog.test.js b/tests/blog.test.js
index 814c0cc..dc54a74 100644
--- a/tests/blog.test.js
+++ b/tests/blog.test.js
@@ -162,3 +162,82 @@ describe('favorites', () => {
     expect(result.likes).toEqual(12)
   })
 })
+
+describe('Authors with more blogs', () => {
+  test('More blogs with empty list', () => {
+    const blogs = [{}]
+    const result = listHelper.mostBlogs(blogs)
+    console.log(result)
+    expect(result).toEqual({ author: undefined, entries: 1 })
+  })
+  test('More blogs with one element in the list', () => {
+    const blogs = [
+      {
+        _id: '5a422bc61b54a676234d17fc',
+        title: 'Type wars',
+        author: 'Robert C. Martin',
+        url: 'http://blog.cleancoder.com/uncle-bob/2016/05/01/TypeWars.html',
+        likes: 2,
+        __v: 0,
+      },
+    ]
+    const result = listHelper.mostBlogs(blogs)
+    console.log(result)
+    expect(result).toEqual({ author: 'Robert C. Martin', entries: 1 })
+  })
+  test('More blogs with big list', () => {
+    const blogs = [
+      {
+        _id: '5a422b3a1b54a676234d17f9',
+        title: 'Canonical string reduction',
+        author: 'Edsger W. Dijkstra',
+        url: 'http://www.cs.utexas.edu/~EWD/transcriptions/EWD08xx/EWD808.html',
+        likes: 12,
+        __v: 0,
+      },
+      {
+        _id: '5a422a851b54a676234d17f7',
+        title: 'React patterns',
+        author: 'Michael Chan',
+        url: 'https://reactpatterns.com/',
+        likes: 7,
+        __v: 0,
+      },
+      {
+        _id: '5a422aa71b54a676234d17f8',
+        title: 'Go To Statement Considered Harmful',
+        author: 'Edsger W. Dijkstra',
+        url: 'http://www.u.arizona.edu/~rubinson/copyright_violations/Go_To_Considered_Harmful.html',
+        likes: 5,
+        __v: 0,
+      },
+      {
+        _id: '5a422b891b54a676234d17fa',
+        title: 'First class tests',
+        author: 'Robert C. Martin',
+        url: 'http://blog.cleancoder.com/uncle-bob/2017/05/05/TestDefinitions.htmll',
+        likes: 10,
+        __v: 0,
+      },
+      {
+        _id: '5a422ba71b54a676234d17fb',
+        title: 'TDD harms architecture',
+        author: 'Robert C. Martin',
+        url: 'http://blog.cleancoder.com/uncle-bob/2017/03/03/TDD-Harms-Architecture.html',
+        likes: 0,
+        __v: 0,
+      },
+      {
+        _id: '5a422bc61b54a676234d17fc',
+        title: 'Type wars',
+        author: 'Robert C. Martin',
+        url: 'http://blog.cleancoder.com/uncle-bob/2016/05/01/TypeWars.html',
+        likes: 2,
+        __v: 0,
+      },
+    ]
+    const result = listHelper.mostBlogs(blogs)
+    console.log(result)
+    expect(result).toEqual({ author: 'Robert C. Martin', entries: 3 })
+  })
+})
diff --git a/utils/list_helper.js b/utils/list_helper.js
index 0c7bad2..4ac8036 100644
--- a/utils/list_helper.js
+++ b/utils/list_helper.js
@@ -1,3 +1,5 @@
+const _ = require('lodash')
+
 const dummy = (blogs) => {
   // ...
   return 1
@@ -14,12 +16,27 @@ const favoriteBlog = (blogs) => {
   const reducer = (max, item) => {
     return max.likes > item.likes ? max : item
   }
-  console.log(blogs.reduce(reducer, 0))
+  //   console.log(blogs.reduce(reducer, 0))
   return blogs.length === 0 ? {} : blogs.reduce(reducer, { likes: 0 })
 }
 
+const mostBlogs = (blogs) => {
+  if (blogs.length === 0) return { author: undefined, entries: 1 }
+  else if (blogs.length === 1) return { author: blogs[0].author, entries: 1 }
+  else {
+    const blogsByAuthor = _.groupBy(blogs, 'author')
+    const authorEntries = _.map(blogsByAuthor, (blogs, author) => ({
+      author,
+      entries: blogs.length,
+    }))
+    console.log(_.maxBy(authorEntries, 'entries'))
+    return _.maxBy(authorEntries, 'entries')
+  }
+}
+
 module.exports = {
   dummy,
   totalLikes,
   favoriteBlog,
+  mostBlogs,
 }