diff --git a/NOTES.md b/NOTES.md
index 65eb36c8..19d0ce36 100644
--- a/NOTES.md
+++ b/NOTES.md
@@ -5,6 +5,10 @@ https://github.com/spatie/simple-excel
 https://csv.thephpleague.com/
 
 mongodb
+model schema
+https://www.mongodb.com/docs/drivers/php/laravel-mongodb/v4.x/eloquent-models/schema-builder/
+
+upsert
 https://medium.com/@kaamil.mirza.2002/how-i-learned-to-upsert-millions-of-documents-into-mongodb-with-minimal-overhead-8b7f9404a70c
 https://www.mongodb.com/docs/manual/reference/method/Bulk.find.upsert/