diff --git a/migrate.py b/migrate.py
index 70308570..5f381715 100644
--- a/migrate.py
+++ b/migrate.py
@@ -83,6 +83,14 @@ def topics(export_topics, topics_by_slug, topics_by_oid, cats_data, tags_data):
 	if len(sys.argv) > 2: limit = int(sys.argv[2])
 	print('migrating %d topics...' % limit)
 	counter = 0
+	for tag in tags_data:
+		old_id = tag["createdBy"]
+		tag["createdBy"] = user_id_map.get(old_id, 0)
+		topic = migrateTag(tag)
+		topics_by_title[topic['title']] = topic
+		topics_by_oid[topic['tag_id']] = topic
+		if not topics_by_slug.get(topic['slug']): topics_by_slug[topic['slug']] = topic
+		counter += 1
 	for cat in cats_data:
 		old_id = cat["createdBy"]
 		# cat["createdBy"] = user_id_map[old_id]
@@ -90,15 +98,9 @@ def topics(export_topics, topics_by_slug, topics_by_oid, cats_data, tags_data):
 		except Exception as e: raise e
 		topics_by_oid[topic['cat_id']] = topic
 		topics_by_slug[topic['slug']] = topic
+		topics_by_title[topic['title']] = topic
 		counter += 1
-	for tag in tags_data:
-		old_id = tag["createdBy"]
-		tag["createdBy"] = user_id_map.get(old_id, 0)
-		topic = migrateTag(tag)
-		topics_by_oid[topic['tag_id']] = topic
-		if not topics_by_slug.get(topic['slug']): topics_by_slug[topic['slug']] = topic
-		counter += 1
-	export_topics = dict(topics_by_slug.items()) # sorted(topics_by_slug.items(), key=lambda item: str(item[1]['createdAt']))) # NOTE: sorting does not work :)
+	export_topics = dict(topics_by_title.items())
 
 def shouts(content_data, shouts_by_slug, shouts_by_oid):
 	''' migrating content items one by one '''
diff --git a/migration/content/.DS_Store b/migration/content/.DS_Store
deleted file mode 100644
index 5b679579..00000000
Binary files a/migration/content/.DS_Store and /dev/null differ
diff --git a/migration/content/article/.gitkeep b/migration/content/article/.gitkeep
deleted file mode 100644
index e69de29b..00000000
diff --git a/migration/content/image/.gitkeep b/migration/content/image/.gitkeep
deleted file mode 100644
index e69de29b..00000000
diff --git a/migration/content/music/.gitkeep b/migration/content/music/.gitkeep
deleted file mode 100644
index e69de29b..00000000
diff --git a/migration/content/prose/.gitkeep b/migration/content/prose/.gitkeep
deleted file mode 100644
index e69de29b..00000000
diff --git a/migration/content/video/.gitkeep b/migration/content/video/.gitkeep
deleted file mode 100644
index e69de29b..00000000
diff --git a/resolvers/__init__.py b/resolvers/__init__.py
index 736682fe..7d164795 100644
--- a/resolvers/__init__.py
+++ b/resolvers/__init__.py
@@ -7,7 +7,8 @@ from resolvers.topics import topic_subscribe, topic_unsubscribe, topics_by_autho
 	topics_by_community, topics_by_slugs
 from resolvers.comments import create_comment, delete_comment, update_comment, rate_comment
 from resolvers.collab import get_shout_proposals, create_proposal, delete_proposal, \
-	update_proposal, rate_proposal, decline_proposal, disable_proposal, accept_proposal
+	update_proposal, rate_proposal, decline_proposal, disable_proposal, accept_proposal, \
+		invite_author, remove_author
 from resolvers.editor import create_shout, delete_shout, update_shout
 from resolvers.community import create_community, delete_community, get_community, get_communities
 
@@ -72,5 +73,7 @@ __all__ = [
 	"disable_proposal",
 	"accept_proposal",
 	"decline_proposal",
-	"delete_proposal"
+	"delete_proposal",
+	"invite_author",
+	"remove_author"
 	]
diff --git a/resolvers/collab.py b/resolvers/collab.py
index 733fbf7a..8131cc51 100644
--- a/resolvers/collab.py
+++ b/resolvers/collab.py
@@ -189,3 +189,56 @@ async def decline_proposal(_, info, id):
 	await ProposalStorage.put(result)
 
 	return {}
+
+
+@mutation.field("inviteAuthor")
+@login_required
+async def invite_author(_, author_slug, shout):
+	auth = info.context["request"].auth
+	user_id = auth.user_id
+
+	with local_session() as session:
+		shout = session.query(Shout).filter(Shout.slug == shout).first()
+		if not shout:
+			return {"error": "invalid shout slug"}
+		authors = [author.id for author in shout.authors]
+		if user_id not in authors:
+			return {"error": "access denied"}
+		author = session.query(User).filter(User.slug == author_slug).first()
+		if author.id in authors:
+			return {"error": "already added"}
+		shout.authors.append(author)
+		session.commit()
+
+	# result = Result("INVITED")
+	# FIXME: await ShoutStorage.put(result)
+
+	# TODO: email notify
+
+	return {}
+
+@mutation.field("removeAuthor")
+@login_required
+async def invite_author(_, author_slug, shout):
+	auth = info.context["request"].auth
+	user_id = auth.user_id
+
+	with local_session() as session:
+		shout = session.query(Shout).filter(Shout.slug == shout).first()
+		if not shout:
+			return {"error": "invalid shout slug"}
+		authors = [author.id for author in shout.authors]
+		if user_id not in authors:
+			return {"error": "access denied"}
+		author = session.query(User).filter(User.slug == author_slug).first()
+		if author.id not in authors:
+			return {"error": "not in authors"}
+		shout.authors.remove(author)
+		session.commit()
+
+	# result = Result("INVITED")
+	# FIXME: await ShoutStorage.put(result)
+
+	# TODO: email notify
+
+	return {}
\ No newline at end of file
diff --git a/schema.graphql b/schema.graphql
index 81ee53a4..a5b77615 100644
--- a/schema.graphql
+++ b/schema.graphql
@@ -137,6 +137,10 @@ type Mutation {
   updateCommunity(community: CommunityInput!): Community!
   deleteCommunity(id: Int!): Result!
 
+  # collab
+  inviteAuthor(author: String!, shout: String!): Result!
+  removeAuthor(author: String!, shout: String!): Result!
+  
   # proposal
   createProposal(body: String!, range: String): Proposal!
   updateProposal(body: String!, range: String): Proposal!