diff --git a/weed/s3api/filer_multipart.go b/weed/s3api/filer_multipart.go
index 783435b40..6989d3f5a 100644
--- a/weed/s3api/filer_multipart.go
+++ b/weed/s3api/filer_multipart.go
@@ -206,6 +206,8 @@ type ListPartsResult struct {
 }
 
 func (s3a *S3ApiServer) listObjectParts(input *s3.ListPartsInput) (output *ListPartsResult, code ErrorCode) {
+	// https://docs.aws.amazon.com/AmazonS3/latest/API/API_ListParts.html
+
 	output = &ListPartsResult{
 		Bucket:           input.Bucket,
 		Key:              objectKey(input.Key),