diff --git a/lesson_10/libraries/src/lesson10.test.ts b/lesson_10/libraries/src/lesson10.test.ts
index bf3c8994b..622859725 100644
--- a/lesson_10/libraries/src/lesson10.test.ts
+++ b/lesson_10/libraries/src/lesson10.test.ts
@@ -62,6 +62,14 @@ describe('Lesson10Test', () => {
       }
       const items = await loader.loadData();
       expect(items.filter((i) => i.getCredits().length).length).toBe(100);
+
+      // Every item that has credits should have the right credits.
+      const itemsWithCredits = items.filter((i) => i.getCredits().length);
+      expect(
+        itemsWithCredits.every((i) =>
+          i.getCredits().every((c) => c.getMediaItemId() === i.getId()),
+        ),
+      ).toBe(true);
     }
   });
 });
diff --git a/lesson_10/libraries/src/models/credit.ts b/lesson_10/libraries/src/models/credit.ts
index fb9cee262..cbf3e7ba1 100644
--- a/lesson_10/libraries/src/models/credit.ts
+++ b/lesson_10/libraries/src/models/credit.ts
@@ -1,13 +1,25 @@
 import { Role } from './role.js';
 
 export class Credit {
-  mediaItemId: string;
-  name: string;
-  role: Role;
+  private mediaItemId: string;
+  private name: string;
+  private role: Role;
 
   constructor(mediaItemId: string, name: string, role: Role) {
     this.mediaItemId = mediaItemId;
     this.name = name;
     this.role = role;
   }
+
+  getMediaItemId(): string {
+    return this.mediaItemId;
+  }
+
+  getName(): string {
+    return this.name;
+  }
+
+  getRole(): Role {
+    return this.role;
+  }
 }
diff --git a/lesson_10/libraries/src/models/media_collection.ts b/lesson_10/libraries/src/models/media_collection.ts
index bde07fb17..9209be969 100644
--- a/lesson_10/libraries/src/models/media_collection.ts
+++ b/lesson_10/libraries/src/models/media_collection.ts
@@ -13,55 +13,59 @@ export class MediaCollection {
   }
 
   search(criteria?: SearchCriteria): ReadonlySet<MediaItem> {
-    const items = [...this.items.values()];
-    if (!criteria) {
-      return new Set(items);
+    if (criteria?.title) {
+      return this.searchByTitle(criteria.title);
     }
-    const title = criteria.title;
-    if (title) {
-      return new Set(items.filter((item) => item.getTitle().includes(title)));
+    if (criteria?.releaseYear) {
+      return this.searchByReleaseYear(criteria.releaseYear);
     }
-    if (criteria.releaseYear) {
-      return new Set(
-        items.filter((item) => item.getReleaseYear() === criteria.releaseYear),
-      );
+    if (criteria?.type) {
+      return this.searchByType(criteria.type);
     }
-    if (criteria.type) {
-      return new Set(items.filter((item) => item.getType() === criteria.type));
+    if (criteria?.creditName) {
+      return this.searchByCreditName(criteria.creditName);
     }
-    if (criteria.creditName) {
-      return new Set(
-        items.filter((item) =>
-          [...item.getCredits()].some(
-            (credit) => credit.name === criteria.creditName,
-          ),
-        ),
-      );
-    }
-    return new Set(items);
+    return new Set(this.getItems());
   }
 
-  searchByTitle(title: string): MediaItem[] {
-    return [...this.items.values()].filter((item) =>
-      item.getTitle().includes(title),
+  searchByTitle(title: string): ReadonlySet<MediaItem> {
+    return new Set(
+      this.getItems().filter((item) =>
+        item
+          .getTitle()
+          .toLowerCase()
+          .includes(title?.toLowerCase() ?? ''),
+      ),
     );
   }
 
-  searchByReleaseYear(releaseYear: number): MediaItem[] {
-    return [...this.items.values()].filter(
-      (item) => item.getReleaseYear() === releaseYear,
+  searchByReleaseYear(releaseYear: number): ReadonlySet<MediaItem> {
+    return new Set(
+      this.getItems().filter((item) => item.getReleaseYear() === releaseYear),
     );
   }
 
-  searchByType(type: string): MediaItem[] {
-    return [...this.items.values()].filter((item) => item.getType() === type);
+  searchByType(type: string): ReadonlySet<MediaItem> {
+    return new Set(this.getItems().filter((item) => item.getType() === type));
   }
 
-  searchByCreditName(name: string): MediaItem[] {
-    return [...this.items.values()].filter((item) =>
-      [...item.getCredits()].some((credit) => credit.name === name),
+  searchByCreditName(name: string): ReadonlySet<MediaItem> {
+    return new Set(
+      this.getItems().filter((item) =>
+        item.getCredits().some((credit) =>
+          credit
+            .getName()
+            .toLowerCase()
+            .includes(name?.toLowerCase() ?? ''),
+        ),
+      ),
     );
   }
+
+  private getItems(): readonly MediaItem[] {
+    return [...this.items.values()];
+  }
+
   getInfo() {
     return {
       getItems: () => [...this.items] as readonly [string, MediaItem][],