Apollo Command Module Entry Monitor System photo
NASA
1976
<a rel="nofollow" class="external free" href="https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19760019156.pdf">https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19760019156.pdf</a> NASA TN D-8249 Apollo Experience Report - Guidance And Control Systems, Raymond E. Wilson, Jr., June 1976