Make NewCommonAttributes public

source.go

@@ -25,7 +25,7 @@ type Source struct {
 
 // NewSource creates a new Source. It returns a *Source.
 func NewSource() *Source {
-	return &Source{CommonAttributes: newCommonAttributes()}
+	return &Source{CommonAttributes: NewCommonAttributes()}
 }
 
 // AddAuthor adds the Person as an author to the Source. It returns its index as