Apollo Flight Director Attitude Indicator
NASA
2009-01-01
Apollo Guidance, Navigation, and Control (GNC) Hardware Overview,  <a rel="nofollow" class="external free" href="https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090016290.pdf">https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090016290.pdf</a>