This article incorporates text that is a public domain work of the United States Government.

The English text became a public domain work in the United States, and in 2006 the international copyright expired.

This article incorporates text from www.safetyboard.nl, a public domain work of the Dutch government.

Pareidolix is released as a public domain work.

This article incorporates text from the public domain work, .

Claiming copyright ownership by publishing a public domain work in a different medium.

This article has public domain work of the United States Government from references.

The novel is now a public domain work.

This article incorporates public domain work of the United States Government from the reference.

This article is originally based on public domain work produced by the U.S. Army.