diff --git a/core/src/main/kotlin/com/insanusmokrassar/postssystem/core/api/PostsAPI.kt b/core/src/main/kotlin/com/insanusmokrassar/postssystem/core/api/PostsAPI.kt
deleted file mode 100644
index 9021fe6a..00000000
--- a/core/src/main/kotlin/com/insanusmokrassar/postssystem/core/api/PostsAPI.kt
+++ /dev/null
@@ -1,3 +0,0 @@
-package com.insanusmokrassar.postssystem.core.api
-
-interface PostsAPI : ReadPostsAPI, WritePostsAPI
diff --git a/core/src/main/kotlin/com/insanusmokrassar/postssystem/core/content/Content.kt b/core/src/main/kotlin/com/insanusmokrassar/postssystem/core/content/Content.kt
index 4d722930..c21ffb42 100644
--- a/core/src/main/kotlin/com/insanusmokrassar/postssystem/core/content/Content.kt
+++ b/core/src/main/kotlin/com/insanusmokrassar/postssystem/core/content/Content.kt
@@ -10,7 +10,7 @@ interface Content
 /**
  * Content which is already registered in database. Using its [id] you can retrieve all known
  * [com.insanusmokrassar.postssystem.core.post.RegisteredPost]s by using
- * [com.insanusmokrassar.postssystem.core.api.ReadPostsAPI.getPostsByContent]
+ * [com.insanusmokrassar.postssystem.core.post.api.ReadPostsAPI.getPostsByContent]
  */
 interface RegisteredContent : Content {
     val id: ContentId
diff --git a/core/src/main/kotlin/com/insanusmokrassar/postssystem/core/post/Post.kt b/core/src/main/kotlin/com/insanusmokrassar/postssystem/core/post/Post.kt
index ded1c2b0..15814a68 100644
--- a/core/src/main/kotlin/com/insanusmokrassar/postssystem/core/post/Post.kt
+++ b/core/src/main/kotlin/com/insanusmokrassar/postssystem/core/post/Post.kt
@@ -1,29 +1,26 @@
 package com.insanusmokrassar.postssystem.core.post
 
-import com.insanusmokrassar.postssystem.core.content.Content
-import com.insanusmokrassar.postssystem.core.content.RegisteredContent
-import kotlinx.serialization.Serializable
+import com.insanusmokrassar.postssystem.core.content.*
 import org.joda.time.DateTime
 
 typealias PostId = String
-typealias PostContents = List<Content>
-typealias RegisteredPostContents = List<RegisteredContent>
+typealias ContentIds = List<ContentId>
 
 /**
  * Base interface for creating of new post. Usually, it is just [SimplePost] instance
  */
 interface Post {
-    val content: PostContents
+    val content: ContentIds
 }
 
 /**
- * Root entity of whole system. Can be retrieved from [com.insanusmokrassar.postssystem.core.api.ReadPostsAPI] by
- * getting and created in [com.insanusmokrassar.postssystem.core.api.WritePostsAPI] by inserting of [Post] instance
+ * Root entity of whole system. Can be retrieved from [com.insanusmokrassar.postssystem.core.post.api.ReadPostsAPI] by
+ * getting and created in [com.insanusmokrassar.postssystem.core.post.api.WritePostsAPI] by inserting of [Post] instance
  */
 interface RegisteredPost : Post {
     val id: PostId
 
-    override val content: RegisteredPostContents
+    override val content: ContentIds
 
     val creationDate: DateTime
     val modificationDate: DateTime
@@ -34,7 +31,7 @@ interface RegisteredPost : Post {
  * is [Post] too, but it is not direct [Post] realisation
  */
 data class SimplePost(
-    override val content: PostContents
+    override val content: ContentIds
 ) : Post
 
 /**
@@ -42,7 +39,7 @@ data class SimplePost(
  */
 data class SimpleRegisteredPost(
     override val id: PostId,
-    override val content: RegisteredPostContents,
+    override val content: ContentIds,
     override val creationDate: DateTime,
     override val modificationDate: DateTime = creationDate
 ) : RegisteredPost
\ No newline at end of file
diff --git a/core/src/main/kotlin/com/insanusmokrassar/postssystem/core/post/api/PostsAPI.kt b/core/src/main/kotlin/com/insanusmokrassar/postssystem/core/post/api/PostsAPI.kt
new file mode 100644
index 00000000..a3fdceea
--- /dev/null
+++ b/core/src/main/kotlin/com/insanusmokrassar/postssystem/core/post/api/PostsAPI.kt
@@ -0,0 +1,3 @@
+package com.insanusmokrassar.postssystem.core.post.api
+
+interface PostsAPI : ReadPostsAPI, WritePostsAPI
diff --git a/core/src/main/kotlin/com/insanusmokrassar/postssystem/core/api/ReadPostsAPI.kt b/core/src/main/kotlin/com/insanusmokrassar/postssystem/core/post/api/ReadPostsAPI.kt
similarity index 95%
rename from core/src/main/kotlin/com/insanusmokrassar/postssystem/core/api/ReadPostsAPI.kt
rename to core/src/main/kotlin/com/insanusmokrassar/postssystem/core/post/api/ReadPostsAPI.kt
index 250d08b1..1ff1e7ca 100644
--- a/core/src/main/kotlin/com/insanusmokrassar/postssystem/core/api/ReadPostsAPI.kt
+++ b/core/src/main/kotlin/com/insanusmokrassar/postssystem/core/post/api/ReadPostsAPI.kt
@@ -1,4 +1,4 @@
-package com.insanusmokrassar.postssystem.core.api
+package com.insanusmokrassar.postssystem.core.post.api
 
 import com.insanusmokrassar.postssystem.core.content.ContentId
 import com.insanusmokrassar.postssystem.core.post.*
diff --git a/core/src/main/kotlin/com/insanusmokrassar/postssystem/core/api/WritePostsAPI.kt b/core/src/main/kotlin/com/insanusmokrassar/postssystem/core/post/api/WritePostsAPI.kt
similarity index 89%
rename from core/src/main/kotlin/com/insanusmokrassar/postssystem/core/api/WritePostsAPI.kt
rename to core/src/main/kotlin/com/insanusmokrassar/postssystem/core/post/api/WritePostsAPI.kt
index c4980197..992f79fd 100644
--- a/core/src/main/kotlin/com/insanusmokrassar/postssystem/core/api/WritePostsAPI.kt
+++ b/core/src/main/kotlin/com/insanusmokrassar/postssystem/core/post/api/WritePostsAPI.kt
@@ -1,4 +1,4 @@
-package com.insanusmokrassar.postssystem.core.api
+package com.insanusmokrassar.postssystem.core.post.api
 
 import com.insanusmokrassar.postssystem.core.post.*
 import com.insanusmokrassar.postssystem.core.post.*
diff --git a/core/src/test/kotlin/com/insanusmokrassar/postssystem/core/api/InMemoryPostsAPI.kt b/core/src/test/kotlin/com/insanusmokrassar/postssystem/core/api/InMemoryPostsAPI.kt
index a6c7baac..00d18702 100644
--- a/core/src/test/kotlin/com/insanusmokrassar/postssystem/core/api/InMemoryPostsAPI.kt
+++ b/core/src/test/kotlin/com/insanusmokrassar/postssystem/core/api/InMemoryPostsAPI.kt
@@ -1,4 +1,4 @@
-package com.insanusmokrassar.postssystem.core.api
+package com.insanusmokrassar.postssystem.core.post.api
 
 import com.insanusmokrassar.postssystem.core.content.ContentId
 import com.insanusmokrassar.postssystem.core.content.RegisteredContent