Fries, Colin (March 13, 2015). "Chronology of Wakeup Calls"(PDF). History Division. NASA. Archived(PDF) from the original on January 5, 2021. Retrieved January 5, 2021. This article incorporates text from this source, which is in the public domain.
web.archive.org
Fries, Colin (March 13, 2015). "Chronology of Wakeup Calls"(PDF). History Division. NASA. Archived(PDF) from the original on January 5, 2021. Retrieved January 5, 2021. This article incorporates text from this source, which is in the public domain.