關於「Standard postcard size」標籤，搜尋引擎有相關的訊息討論：

Postcard Specifications - Postal Serviceswww.post.gov.tw › post › internet › U_english2Your Guide to Standard Postcard Sizes and Dimensionswww.catdi.com › your-guide-to-standard-postcard-sizes-an...What is the size of a post card photo? - Quorawww.quora.com › What-is-the-size-o