因为根据万国邮政公约，邮票不得贴在明信片背面。

Because according to the International Postal Convention, it is not allowed to affix stamps on its back.

youdao

因为根据万国邮政公约，邮票不得贴在明信片背面。

Because according to the International Postal Convention, it is not allowed to affix stamps on its back.

youdao