[1] NullとEmptyとNothingと""(長さ0の文字列)の違い - AccessVBA モーグ即効テクニック集 <http://www.moug.net/tech/acvba/0050010.htm> (名無しさん)
[2] Breaking: refactor structured clone into serialize/deserialize (domenic著, 3/20/2017, 9:09:33 PM) <https://github.com/whatwg/html/commit/97d644c97335956610a31e8ad98d1a388c063e84>
Google search: Null (Visual Basic)