diff --git a/.gitignore b/.gitignore
index b04a8c8..1906a38 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,3 +9,6 @@
 
 # rspec failure tracking
 .rspec_status
+Gemfile.lock
+.vscode/
+bin/rspec
diff --git a/lib/ieee/idams/publication_info.rb b/lib/ieee/idams/publication_info.rb
index fd95c0a..5fea8b1 100644
--- a/lib/ieee/idams/publication_info.rb
+++ b/lib/ieee/idams/publication_info.rb
@@ -75,7 +75,7 @@ class PublicationInfo < Lutaml::Model::Serializable
 
       # Standard relationship
       # @return [String] standard relationship
-      attribute :standard_relationship, StandardRelationship
+      attribute :standard_relationship, StandardRelationship, collection: true
 
       # Standard modifier set
       # @return [StandardModifierSet] standard modifier details