Translation of "подписано" in English

Это письмо не подписано.

- This letter is not signed.
- This letter isn't signed.

У нас подписано соглашение.

We have a signed agreement.

Письмо было подписано Дэном.

The letter was signed by Dan.

Письмо было подписано Томом.

The letter was signed by Tom.

Это должно быть подписано в присутствии трёх свидетелей.

This must be signed in the presence of three witnesses.

Разве не очень интересная ситуация? Подписано соглашение о нейтралитете с подписями 53 стран

Isn't there a very interesting situation? Neutrality agreement signed with 53 countries' signatures